WO2015080502A1 - Active material for all-solid lithium secondary battery, method for manufacturing same, and all-solid lithium secondary battery comprising same - Google Patents

Active material for all-solid lithium secondary battery, method for manufacturing same, and all-solid lithium secondary battery comprising same Download PDF

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WO2015080502A1
WO2015080502A1 PCT/KR2014/011508 KR2014011508W WO2015080502A1 WO 2015080502 A1 WO2015080502 A1 WO 2015080502A1 KR 2014011508 W KR2014011508 W KR 2014011508W WO 2015080502 A1 WO2015080502 A1 WO 2015080502A1
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lithium
active material
solid
secondary battery
coating layer
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PCT/KR2014/011508
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French (fr)
Korean (ko)
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신동욱
김정훈
김우섭
최선호
이영민
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한양대학교 산학협력단
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Priority to US15/100,130 priority Critical patent/US10050258B2/en
Priority to CN201480065414.0A priority patent/CN105830260B/en
Publication of WO2015080502A1 publication Critical patent/WO2015080502A1/en

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    • H—ELECTRICITY
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    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/131—Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01D—COMPOUNDS OF ALKALI METALS, i.e. LITHIUM, SODIUM, POTASSIUM, RUBIDIUM, CAESIUM, OR FRANCIUM
    • C01D15/00—Lithium compounds
    • C—CHEMISTRY; METALLURGY
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    • C01D—COMPOUNDS OF ALKALI METALS, i.e. LITHIUM, SODIUM, POTASSIUM, RUBIDIUM, CAESIUM, OR FRANCIUM
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    • C01D15/08—Carbonates; Bicarbonates
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    • C01G45/00—Compounds of manganese
    • C01G45/12—Manganates manganites or permanganates
    • C01G45/1221—Manganates or manganites with a manganese oxidation state of Mn(III), Mn(IV) or mixtures thereof
    • C01G45/1228—Manganates or manganites with a manganese oxidation state of Mn(III), Mn(IV) or mixtures thereof of the type [MnO2]n-, e.g. LiMnO2, Li[MxMn1-x]O2
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    • C01G53/40—Nickelates
    • C01G53/42—Nickelates containing alkali metals, e.g. LiNiO2
    • C01G53/44—Nickelates containing alkali metals, e.g. LiNiO2 containing manganese
    • C01G53/50—Nickelates containing alkali metals, e.g. LiNiO2 containing manganese of the type [MnO2]n-, e.g. Li(NixMn1-x)O2, Li(MyNixMn1-x-y)O2
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    • H01M10/052—Li-accumulators
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    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0561—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of inorganic materials only
    • H01M10/0562—Solid materials
    • H—ELECTRICITY
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    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M10/4235—Safety or regulating additives or arrangements in electrodes, separators or electrolyte
    • H—ELECTRICITY
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    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/139—Processes of manufacture
    • H01M4/1391—Processes of manufacture of electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
    • H—ELECTRICITY
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    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H01M4/366—Composites as layered products
    • H—ELECTRICITY
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    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/50—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese
    • H01M4/505—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy
    • H—ELECTRICITY
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    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
    • H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2002/00—Crystal-structural characteristics
    • C01P2002/50—Solid solutions
    • C01P2002/52—Solid solutions containing elements as dopants
    • C01P2002/54—Solid solutions containing elements as dopants one element only
    • C—CHEMISTRY; METALLURGY
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    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2002/00—Crystal-structural characteristics
    • C01P2002/70—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data
    • C01P2002/72—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data by d-values or two theta-values, e.g. as X-ray diagram
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    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00—Particle morphology
    • C01P2004/01—Particle morphology depicted by an image
    • C01P2004/03—Particle morphology depicted by an image obtained by SEM
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    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
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    • C01P2004/60—Particles characterised by their size
    • C01P2004/61—Micrometer sized, i.e. from 1-100 micrometer
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
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    • C01P2004/80—Particles consisting of a mixture of two or more inorganic phases
    • C—CHEMISTRY; METALLURGY
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    • C01P2006/00—Physical properties of inorganic compounds
    • C01P2006/40—Electric properties
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present invention relates to an active material for an all-solid-state lithium secondary battery having excellent cycle and rate characteristics, and more particularly, to an oxide active material surface-treated with a lithium-based compound, a method for preparing the same, and an interface method in a solid electrolyte by employing the same. It is related with the all solid lithium secondary battery which can be suppressed.
  • Lithium ion secondary batteries using organic liquid electrolytes have been widely used in small electronic devices because they exhibit excellent energy and power density characteristics compared to other energy storage devices.
  • the interface resistance is greatly increased due to the interfacial reaction such as the formation of a resistive layer due to the diffusion of metal elements or the formation of a lithium deficient layer due to a potential difference. As a result, the cycle and rate characteristics are greatly reduced.
  • Li 1 + x (M) O 2 (M is a transition metal including Co, Mn, Ni, or these X is 0 to 1 or less), and transition metal oxides such as Al 2 O 3 , ZrO, SiO 2 , lithium transition metal oxides such as Li 4 Ti 5 O 12 , LiNbO 3, and Li 2
  • M is a transition metal including Co, Mn, Ni, or these X is 0 to 1 or less
  • transition metal oxides such as Al 2 O 3 , ZrO, SiO 2
  • lithium transition metal oxides such as Li 4 Ti 5 O 12 , LiNbO 3, and Li 2
  • the active material coating technology for suppressing side reactions occurring at the interface is an additional coating process using a metal element-containing starting material to increase the process cost, difficulty in precise composition control of the coating material, optimization of the diffusion coefficient of lithium ions of the coating material There are various variables such as the complicated coating process conditions. Therefore, the selection of coating materials is very limited, and coating materials and processing techniques that are more suitable for all-solid-state batteries are required.
  • the present invention is to provide a cathode active material for an all-solid-state lithium secondary battery that can improve the battery characteristics by effectively inhibiting the interfacial reaction between the sulfide-based solid electrolyte and the electrode in the all-solid-state lithium secondary battery.
  • the present invention is to provide a positive electrode active material for an all-solid lithium secondary battery and an all-solid lithium secondary battery including the same.
  • an object of the present invention is to provide a method of manufacturing a cathode active material for an all-solid-state lithium secondary battery.
  • the present invention provides an anode active material for an all-solid-state lithium secondary battery comprising an oxide represented by the following [Formula 1] and a lithium compound coating layer formed while surrounding the surface of the oxide particles.
  • M is a transition metal comprising Co, Mn or Ni or mixtures thereof, x is 0 ⁇ x ⁇ 1, preferably 0.10 ⁇ x ⁇ 0.20.
  • the lithium compound coating layer is characterized by consisting of at least one selected from lithium compounds, such as lithium salts including lithium hydroxide (LiOH) and lithium carbonate (Li 2 CO 3 ).
  • the present invention provides an all-solid-state lithium secondary battery comprising a sulfide-based solid electrolyte and an electrode including the cathode active material according to the present invention.
  • the present invention may form a lithium compound coating layer at the same time in the active material synthesis process, and provides a method for producing a positive electrode active material that can form a lithium compound coating layer through the secondary process to the active material synthesized, the coating layer is on the surface Compared with the active material, it can suppress the formation of the resistive layer due to the diffusion of the transition metal element of the active material or the formation of the lithium deficiency layer due to the potential difference, and have a wider diffusion path of lithium ions due to the improved contact area between the active material and the electrolyte. It provides a positive electrode active material.
  • Method for producing a positive electrode active material according to the invention is characterized in that it comprises the following steps, respectively.
  • the surface of the cathode active material for an all-solid-state lithium secondary battery manufactured by this is surrounded by a lithium compound coating layer, and the lithium compound coating layer is formed on the surface simultaneously with the synthesis of the cathode active material.
  • the lithium precursor may be selected from lithium nitrate, lithium hydroxide, lithium citrate, lithium acetate, lithium sulfate and lithium carbonate
  • the metal salt includes Co, Ni or Mn It may be at least one selected from nitrate, acetate or citrate of the transition metal.
  • step (b) may be performed by heating to a temperature of 40-250 °C.
  • the lithium compound coating layer may be made of at least one selected from lithium compounds such as lithium salts including lithium hydroxide (LiOH) and lithium carbonate (Li 2 CO 3 ), preferably
  • the lithium compound coating layer may be lithium carbonate (Li 2 CO 3 ), and the lithium carbonate may be used when the heat treatment of step (c) is performed in a complex gas atmosphere including carbon dioxide (CO 2 ) or carbon dioxide. It may be formed.
  • the method of manufacturing a cathode active material capable of forming a lithium compound coating layer through a secondary process on the active material synthesized according to the present invention includes the following steps.
  • the surface of the oxide active material is characterized by surrounding the lithium compound coating layer.
  • M is a transition metal including Co, Mn, or Ni, or a mixture thereof, and X is 0 ⁇ X ⁇ 1.
  • the lithium precursor may be selected from lithium nitrate, lithium hydroxide, lithium citrate, lithium acetate, lithium sulfate and lithium carbonate
  • the lithium compound coating layer is the lithium compound coating layer It may be made of one or more selected from lithium compounds such as lithium salts including lithium hydroxide (LiOH) and lithium carbonate (Li 2 CO 3 ).
  • the positive electrode active material of the all-solid-state lithium secondary battery according to the present invention is characterized in that the coating layer made of a lithium compound is formed surrounding the particle surface, the coating layer is a functional layer to suppress the interfacial reaction between the sulfide-based solid electrolyte and the electrode Can significantly improve battery characteristics.
  • the positive electrode active material according to the present invention is a charge and discharge process when the battery composition compared to the active material without a coating layer on the surface by forming a lithium compound coating layer on the active material in which the lithium compound coating layer is simultaneously formed or synthesized in the active material synthesis process through a secondary process It can suppress the formation of the resistive layer due to the diffusion of the transition metal element of the active material, or the formation of a lithium deficient layer due to the potential difference, and can have a wide diffusion path of lithium ions due to the improved contact area between the active material and the electrolyte.
  • the coating layer is formed at the same time in the active material synthesis process, the post-layer coating process for inhibiting the interfacial reaction is not required separately can shorten the production process It also has the advantage.
  • Li 2 CO 3 lithium compound synthesized according to Synthesis Examples 1 and 4 of the present invention, respectively (b (In-situ), d (Ex- situ), which is an image compared with an SEM image of a lithium cobalt oxide active material (a, c in FIG. 1) with no surface coated.
  • FIG. 4 shows charge and discharge curves of an all-solid-state battery for lithium cobalt oxide active materials synthesized by adjusting the amounts of lithium precursors of lithium precursors in Synthesis Example 1 to 10 wt%, 20 wt%, and 30 wt%, respectively. It is a graph.
  • FIG. 5 is an electrochemical charge and discharge of an all-solid-state battery for a lithium cobalt oxide active material coated with a lithium compound coated with a lithium compound having a ratio of 1.2: 1 to lithium and cobalt in a synthesis example 1 of the present invention.
  • FIG. 6 is a graph showing charge and discharge life characteristics of an all-solid-state battery with respect to a lithium cobalt oxide active material coated with a lithium compound by varying the proportion of lithium according to Synthesis Example 1 of the present invention.
  • FIG. 8 is a graph showing charge and discharge curves of an all-solid-state battery for a lithium nickel cobalt oxide active material synthesized according to Synthesis Example 3 of the present invention and a lithium nickel cobalt oxide active material not coated on its surface.
  • FIG. 9 is a charge of an all-solid-state battery for active materials coated with a lithium compound on a surface using various precursors to commercial lithium cobalt oxide and a commercial lithium cobalt oxide active material not coated on the surface according to Synthesis Example 4 of the present invention. It is a graph showing a discharge curve.
  • FIG. 10 is a charge of an all-solid-state battery for active materials coated with a lithium compound on the surface using various precursors to commercial lithium cobalt oxide and a commercial lithium cobalt oxide active material not coated on the surface according to Synthesis Example 4 of the present invention. It is a graph showing capacity characteristics when the discharge rate is changed.
  • 11 is a commercial lithium nickel-cobalt-manganese (6: 2: 2) active material coated with a lithium compound on the surface of a commercially available lithium nickel-cobalt-manganese (6: 2: 2) according to Synthesis Example 5 of the present invention. 2) A graph showing charge and discharge curves of an all-solid-state battery with respect to the oxide active material.
  • the present invention relates to an oxide active material surface-treated with a lithium compound, a method for producing the same, and an all-solid-state lithium secondary battery capable of effectively suppressing an interfacial reaction in a solid electrolyte by employing the same.
  • the positive electrode active material according to the present invention is formed with a coating layer made of a lithium compound surrounding the particle surface to form a sulfide-based solid electrolyte.
  • an excessive amount of lithium source is added during the manufacturing process to intentionally form a coating layer of impurities on the surface of the active material by the lithium source remaining after synthesis, thereby inhibiting the interfacial reaction with the sulfide-based solid electrolyte unlike the liquid electrolyte system. It is characterized in that it serves as a coating functional layer.
  • the prepared active material can occlude and release lithium
  • the mixture resulting from the excess lithium salt remaining after synthesis on the surface of the particle having a structure is coated on the surface to form a coating layer.
  • the active material and the lithium salt are dissolved in a solvent by stirring and drying and heat-treating them, and the prepared active material has a structure capable of occluding and releasing lithium.
  • the mixture resulting from the excess lithium salt remaining after synthesis on the particle surface is coated on the surface to form a coating layer.
  • the interfacial reaction with the sulfide-based solid electrolyte is suppressed by the lithium compound coating layer formed on the surface of the active material according to the present invention, thereby forming a resistance layer due to diffusion of the transition metal element of the active material during battery construction.
  • the lithium deficiency layer may be suppressed due to the potential difference and may have a broad diffusion path of lithium ions due to the improved contact area between the active material and the electrolyte.
  • One aspect of the present invention is the all-solid lithium secondary battery using a sulfide-based solid electrolyte for all-solid lithium secondary battery that can improve the battery characteristics by inhibiting the interfacial reaction between the electrode and the sulfide-based solid electrolyte to implement excellent cycle and rate characteristics
  • An active material includes an oxide represented by the following [Formula 1] and a lithium compound coating layer formed while surrounding the surface of the oxide particles.
  • M is a transition metal including Co, Mn or Ni or a mixture thereof
  • X is 0 ⁇ X ⁇ 1, preferably 0.10 ⁇ X ⁇ 0.20.
  • the lithium compound coating layer is characterized in that it is made of at least one selected from lithium compounds, such as lithium salts including lithium hydroxide (LiOH) and lithium carbonate (Li 2 CO 3 ), in one material constituting the coating layer
  • lithium salts may be selected from lithium nitrate, lithium hydroxide, lithium citrate, lithium acetate, lithium sulfate and lithium carbonate.
  • Another aspect of the present invention relates to a method for producing an active material for an all-solid-state lithium secondary battery having the composition, structure, and characteristics as described above.
  • a lithium salt and a transition metal salt is dissolved in a solvent by stirring to prepare a solution, which is prepared by drying and heat treatment, and the prepared active material has a structure capable of occluding and releasing lithium
  • the mixture produced from the excess lithium salt remaining after synthesis on the surface of the particles having a has a form to coat the surface to form a coating layer.
  • the active material and the lithium salt are dissolved in a solvent by stirring, and then manufactured by drying and heat treatment, and the prepared active material has a structure capable of occluding and releasing lithium.
  • the mixture produced from the excess lithium salt remaining after synthesis on the surface of the particles having the form is coated on the surface to form a coating layer.
  • the type of the lithium salt is not particularly limited, and may be selected from lithium nitrate, lithium hydroxide, lithium citrate, lithium acetate, lithium sulfate, and lithium carbonate, and the type of transition metal salt is not particularly limited and is intended to be implemented. Depending on the voltage and capacity of the battery, it is possible to apply a mixture containing one or more salts containing transition metals such as Co, Ni and Mn.
  • a lithium salt solution and a transition metal salt solution may be prepared separately, and a transition metal salt solution may be added little by little to the lithium salt solution, or a lithium salt solution may be added little by little to the transition metal salt solution. It can also be prepared by dissolving lithium salt and transition metal salt in one solvent at the same time.
  • the method of preparing the active material is selected based on the precursor solution, but this is only one embodiment of the present invention and may be synthesized from other starting materials using various synthetic methods such as solid phase method, and by-products are added to the surface by adding excessive lithium. If it is a method that can form a not limited.
  • the degree of coating of by-products generated from the excess lithium source on the surface of the prepared active material is controlled by the amount of lithium source added.
  • the addition amount of the lithium source is such that the ratio of Li / Co is 1.0 to 1.5, and the lithium agitation time and temperature are not greatly limited within the conditions in which the solvent can be evaporated after the salt is sufficiently uniformly dissolved.
  • the solvent is dried at 40 ° C. or higher to sufficiently remove the solvent, and then subjected to a post-heat treatment process at a temperature of 600 to 1000 ° C. to prepare an active material having a high crystallinity of a layered structure.
  • the heat treatment temperature and time are freely adjustable according to the desired crystallinity and particle size.
  • an all-solid lithium secondary battery comprising the active material for the all-solid lithium secondary battery and a sulfide-based solid electrolyte.
  • the active material according to the present invention and a sulfide-based solid electrolyte may be mixed to prepare a composite electrode, and a conductive agent may be added to improve electronic conductivity.
  • the mixing method for manufacturing the composite electrode may be performed by a dry or wet method of the solid electrolyte, the active material, and the conductive agent, and the method of forming a uniform distribution among the constituent particles and improving the contact between the particles is not particularly limited. Do not.
  • the shape of the composite electrode may be applied to the top of the solid electrolyte in the form of a powder or coated with Al, Cu, Ti, SUS, etc. on the surface of the metal sheet to form a sheet according to the purpose.
  • the sulfide-based solid electrolyte used in the manufacture of the composite electrode includes Li 2 S, which is a mesh tree, and various sulfide powders such as P 2 S 5 , B 2 S 3 , SiS 2 , and GeS 2 may be used as the network forming body. have.
  • Solid electrolytes can be largely prepared in amorphous and crystalline forms.
  • Solid electrolyte synthesis based on the amorphous system mixes the tree planting body and the tree forming powder to the stoichiometric ratio, and then synthesizes and amorphous by using melt-cooling method or mechanical milling method, and then heat treatment to selectively improve conductivity. Go through the process.
  • the crystalline solid electrolyte is prepared through a solid phase method through high temperature heat treatment under a vacuum or inert gas atmosphere after the sulfide-based powders are mixed in a stoichiometric ratio.
  • the solid electrolyte thus made is used in the electrolyte layer and also mixed with the active material / conductor and binder to provide an ion conducting path in the composite electrode.
  • Synthesis Examples 1 to 3 synthesized the active material coated on the surface of the lithium compound of various compositions simultaneously with the synthesis of the oxide active material.
  • Lithium nitrate (LiNO 3 ) and Cobalt nitrate hexahydrate (Co (NO 3 ) 2 .6H 2 O) are dissolved in water in a molar ratio of 1.1: 1 to 1.3: 1 and then volatilized while stirring. After completely drying the water was synthesized by heat treatment in the air for 5 hours at 800 °C.
  • Lithium hydroxide (LiOH), instead of Lithium nitrate (LiNO 3 ) used in Synthesis Example 1 was synthesized in the same manner as in Synthesis Example 1 except that Lithium hydroxide (LiOH), Lithium acetate CH 3 COO-Li.
  • Synthesis Example 3 Preparation of lithium-nickel-cobalt oxide to replace the lithium cobalt oxide (LiNi 0.02 Co 0.98 O 2) and lithium nickel oxide is a lithium cobalt oxide is coated on the surface (LiNi 0.02 Co 0.98 O 2)
  • Cobalt nitrate hexahydrate (Co (NO 3 ) 2 ⁇ 6H 2 O) instead of the Nickel nitrate hexahydrate (Ni (NO 3 ) 2 ⁇ 6H 2 O) and Cobalt nitrate hexahydrate (Co (NO 3 ) 2 ⁇ 6H 2 O) (0.02 Synthesis was carried out in the same manner as in Synthesis Example 1, except that: a molar ratio of 0.98) was used.
  • Synthesis Examples 4 to 5 below were coated with a lithium compound on the oxide active material is already synthesized to synthesize an active material coated on the surface of the lithium compound of various compositions.
  • the lithium precursor is dissolved in water by calculating the coating amount based on the weight of the active material. After stirring for about 1 hour, the active materials are dispersed together with some heat. After drying completely, the mixture was heat-treated at 600 ° C. for 5 hours for synthesis.
  • Synthesis was carried out in the same manner as in Synthesis Example 4, except that Synthesis Example 4 was used as a lithium nickel-cobalt-manganese oxide active material instead of the lithium cobalt oxide active material.
  • Li 2 S and P 2 S 5 powder was put in a zirconia milling pot and subjected to mechanical milling (MM) to synthesize an amorphous solid electrolyte.
  • MM mechanical milling
  • glass-ceramics powders were prepared through a subsequent heat treatment process under an argon atmosphere of 200 to 300 ° C. to improve ion conductivity.
  • a binder is added.
  • the manufactured composite electrode is coated on a current collector such as a metal or carbon fiber sheet or coated on an electrolyte surface in a cell manufacturing process and then dried at 100 ° C. to 200 ° C. after application.
  • the sulfide-based solid electrolyte is pressurized to 1 ton in a molding mold to form a thin electrolyte layer, and the composite electrode and the carbon fiber sheet current collector are sequentially attached thereto and pressurized to 4 tons. Thereafter, the indium foil was attached to the opposite side using the counter electrode and pressurized again to 3 tons to produce a bulk cell.
  • the prepared pellets were circular with a diameter of 16 mm, and assembled into a 2032 SUS coin cell for battery evaluation.
  • Li 2 CO 3 lithium compound synthesized according to Synthesis Examples 1 and 4 of the present invention, respectively (b (in-situ), d (ex- situ), which is an image compared with an SEM image of a lithium cobalt oxide active material (a, c in FIG. 1) with no surface coated.
  • b is a state where a lithium oxide coating layer is formed on the surface after synthesis
  • c is a commercial lithium cobalt oxide
  • d is a surface of a commercial lithium cobalt oxide The lithium cobalt oxide active material in a state in which a coating layer is formed by post-treatment is shown.
  • the lithium compound is coated in the synthesis process (in-situ) without post-treatment (b of FIG. 1), the particles due to the formation of lithium compounds in the washed state after synthesis (a in FIG. 1) are distributed on the surface. The roughness can be seen.
  • lithium carbonate which is one of the lithium compounds with weak cobalt oxide with strong crystallinity
  • Lithium carbonate Lithium carbonate (Li 2 CO 3 )
  • an atmosphere containing carbon dioxide (CO 2 ) is formed during the heat treatment, residual lithium reacts with the carbon dioxide to form lithium carbonate.
  • the peaks that did not exist in the lithium cobalt oxide (Synthesized & washed) or commercialized (pristine, commercial) after the synthesis was washed in-situ coating It can be seen that the peaks corresponding to lithium carbonate were formed in all of the samples coated or ex-situ coated around 860 cm ⁇ 1, around 1490 cm ⁇ 1 , and around 1520 cm ⁇ 1 .
  • lithium source When synthesizing a lithium cobalt oxide active material by increasing the amount of lithium precursor, a lithium source, to 10 wt%, 20 wt%, and 30 wt%, respectively, lithium, except lithium required for synthesis, acts as an impurity, causing lithium carbonate to remain. do.
  • the amount of lithium carbonate present on the surface is changed according to the amount of residual lithium, and the electrochemical properties are shown to be different by the lithium carbonate coating layer as shown in FIG. 4.
  • a lithium source which is a lithium source
  • a lithium source is synthesized in an excess amount, and depending on the atmosphere, the remaining lithium reacts with other precursors and usually remains as lithium carbonate.
  • lithium carbonate is regarded as an impurity, causing deterioration of cell characteristics.
  • Lithium due to resistance layer formation or potential difference due to diffusion of transition metal elements of the active material with electrolyte through the lithium compound coating on the surface even if the coating using various precursors as a lithium source through comparison with no coating It was confirmed that it inhibits the formation of the deficient layer and induces a diffusion path of wide lithium ions due to the improved contact area between the active material and the electrolyte.
  • the electrochemical charge and discharge characteristics of the all-solid-state battery using a solid electrolyte after the lithium compound coating after the commercial lithium nickel-cobalt-manganese oxide active material was coated were compared.
  • the liquid electrolyte although a commercial lithium nickel-cobalt-manganese oxide active material exhibiting high capacity and stable charge and discharge characteristics was used, all the solid-state batteries showed low capacity when the lithium compound coating was not applied after the post-treatment. After coating the compound it was confirmed to show a high capacity.
  • the lithium compound coating can also improve the electrochemical charge and discharge life characteristics.
  • the positive electrode active material of the all-solid-state lithium secondary battery according to the present invention is characterized in that the coating layer made of a lithium compound is formed surrounding the particle surface, the coating layer is a functional layer to suppress the interfacial reaction between the sulfide-based solid electrolyte and the electrode By working, it is possible to greatly improve the characteristics of the all-solid-state lithium secondary battery can be useful industrially.

Abstract

The present invention relates to an oxide active material surface-treated with a lithium compound, a method for preparing the same, and an all-solid lithium secondary battery capable of effectively suppressing an interface reaction in a solid electrolyte by adopting the same. In the all-solid lithium secondary battery comprising an electrode containing a positive electrode active material and a sulfide-based solid electrolyte, the positive electrode active material according to the present invention can significantly improve battery characteristics since a coating layer formed of a lithium compound is formed while surrounding a particle surface to act as a functional coating layer which suppresses the interface reaction of the sulfide-based solid electrolyte and the electrode. In addition, in cases where the active material is synthesized and coated with a lithium compound at the same time, a lithium salt and a transition metal salt are dissolved in a solvent through stirring, to prepare a solution, followed by drying and heat treatment, and here, the prepared active material has a form in which a mixture generated from an excessive amount of lithium salt which is synthesized and then remains on the particle surface having a structure capable of absorbing and releasing lithium is coated on the particle surface to form a coating layer. In addition, in cases where the previously synthesized active material is coated with a lithium compound, the active material and a lithium salt are dissolved in a solvent through stirring, followed by drying and heat-treatment, and here, the prepared active material has a form in which a mixture generated from an excessive amount of lithium salt which is synthesized and then remains on the particle surface having a structure capable of absorbing and releasing lithium is coated on the particle surface to form a coating layer.

Description

전고체 리튬 이차전지용 활물질, 그 제조방법 및 이를 포함하는 전고체 리튬 이차전지Active material for all-solid lithium secondary battery, manufacturing method and all-solid lithium secondary battery comprising same
본 발명은 우수한 사이클 및 율속 특성을 갖는 전고체 리튬 이차전지용 활물질에 관한 것으로서, 더욱 상세하게는 리튬계 화합물로 표면 처리되어 있는 산화물 활물질과 이의 제조방법 및 이를 채용하여 고체 전해질에서의 계면 반응을 효과적으로 억제할 수 있는 전고체 리튬 이차전지에 관한 것이다.The present invention relates to an active material for an all-solid-state lithium secondary battery having excellent cycle and rate characteristics, and more particularly, to an oxide active material surface-treated with a lithium-based compound, a method for preparing the same, and an interface method in a solid electrolyte by employing the same. It is related with the all solid lithium secondary battery which can be suppressed.
유기 액체 전해질을 사용하는 리튬 이온 이차전지는 다른 에너지 저장 장치에 비하여 우수한 에너지 및 출력 밀도 특성을 나타내어 소형 전자기기에 널리 사용되어 왔다.Lithium ion secondary batteries using organic liquid electrolytes have been widely used in small electronic devices because they exhibit excellent energy and power density characteristics compared to other energy storage devices.
하지만, 최근 들어 소형 전자기기뿐만 아니라 중대형 에너지 저장장치로의 적용범위가 급속하게 확대됨에 따라서 액체 전해질의 누수로 인한 폭발 및 화재 위험이 없는 안전한 전해질 소재에 대한 관심으로 인하여 불연성 무기 고체 전해질을 이용한 전고체 리튬 이차전지에 대한 연구가 활발히 이루어지고 있다. 전고체 리튬 이차전지용 무기 고체 전해질로는 산화물계, 할로이드계 및 황화물계 고체 전해질에 대한 연구가 가장 활발하게 이루어지고 있지만, 월등한 리튬 이온 전도도 특성으로 인해 황화물계 고체 전해질이 가장 기대되는 재료로 주목받고 있다.However, in recent years, as the range of application to medium and large energy storage devices as well as small electronic devices has been rapidly expanded, due to the interest in the safe electrolyte material without the risk of explosion and fire due to leakage of liquid electrolyte, Research on solid lithium secondary batteries is being actively conducted. As inorganic solid electrolytes for all-solid-state lithium secondary batteries, researches on oxide-based, haloid- and sulfide-based solid electrolytes are most actively conducted, but sulfide-based solid electrolytes are the most expected materials due to their superior lithium ion conductivity. It is attracting attention.
그러나, 황화물계 고체 전해질은 기존에 널리 사용되고 있는 산화물계 활물질과 접촉하였을 경우에 금속원소의 확산으로 인한 저항층 형성 또는 포텐셜 차이로 인한 리튬 결핍층 형성 등의 계면 반응으로 인하여 계면 저항이 크게 증가하고, 이로 인하여 사이클 및 율속 특성이 크게 저하되는 문제점을 갖고 있다.However, when the sulfide-based solid electrolyte is in contact with an oxide-based active material, which is widely used, the interface resistance is greatly increased due to the interfacial reaction such as the formation of a resistive layer due to the diffusion of metal elements or the formation of a lithium deficient layer due to a potential difference. As a result, the cycle and rate characteristics are greatly reduced.
따라서, 황화물계 고체 전해질과 산화물계 활물질과의 계면에서 부반응을 억제하고, 사이클 특성과 율속 특성 향상을 위하여 Li1+x(M)O2(M은 Co, Mn, Ni을 포함한 전이 금속 또는 이들의 혼합물이고, x는 0 내지 1 이하)의 산화물계 활물질 표면에 Al2O3, ZrO, SiO2와 같은 전이금속 산화물, Li4Ti5O12, LiNbO3와 같은 리튬 전이금속 산화물, Li2O-SiO2와 같은 산화물 또는 NiS, CoS와 같은 전이금속 황화물 등으로 피복층을 형성함으로서, 금속원소의 확산으로 인한 저항층 형성 또는 포텐셜 차이로 인한 리튬 결핍층 형성과 같은 부반응을 억제하려는 시도가 보고되고 있다.Therefore, in order to suppress side reactions at the interface between the sulfide-based solid electrolyte and the oxide-based active material, and to improve cycle characteristics and rate characteristics, Li 1 + x (M) O 2 (M is a transition metal including Co, Mn, Ni, or these X is 0 to 1 or less), and transition metal oxides such as Al 2 O 3 , ZrO, SiO 2 , lithium transition metal oxides such as Li 4 Ti 5 O 12 , LiNbO 3, and Li 2 By forming a coating layer with an oxide such as O-SiO 2 or a transition metal sulfide such as NiS or CoS, attempts to suppress side reactions such as forming a resistive layer due to diffusion of metal elements or forming a lithium deficient layer due to potential differences have been reported. It is becoming.
다만, 계면에서 일어나는 부반응을 억제하기 위한 상기 활물질 코팅 기술은 금속 원소 함유 출발물질을 사용한 추가 코팅 공정에 의해 공정 단가 상승 및 코팅 소재의 정밀한 조성 제어의 어려움, 코팅소재의 리튬 이온의 확산계수 최적화를 위한 코팅 공정조건이 복잡하다는 점 등 다양한 변수가 있어 코팅 재료의 선택폭이 매우 제한적이며 전고체 전지에 보다 적합한 코팅 소재 및 공정 기술이 요구된다.However, the active material coating technology for suppressing side reactions occurring at the interface is an additional coating process using a metal element-containing starting material to increase the process cost, difficulty in precise composition control of the coating material, optimization of the diffusion coefficient of lithium ions of the coating material There are various variables such as the complicated coating process conditions. Therefore, the selection of coating materials is very limited, and coating materials and processing techniques that are more suitable for all-solid-state batteries are required.
따라서, 본 발명은 전고체 리튬 이차전지에서 황화물계 고체 전해질과 전극간의 계면 반응을 효과적으로 억제하여 전지 특성을 향상시킬 수 있는 전고체 리튬 이차전지용 양극 활물질을 제공하고자 한다.Accordingly, the present invention is to provide a cathode active material for an all-solid-state lithium secondary battery that can improve the battery characteristics by effectively inhibiting the interfacial reaction between the sulfide-based solid electrolyte and the electrode in the all-solid-state lithium secondary battery.
또한, 본 발명에 따른 전고체 리튬 이차전지용 양극 활물질 및 이를 포함하는 전고체 리튬 이차전지를 제공하고자 한다.In addition, the present invention is to provide a positive electrode active material for an all-solid lithium secondary battery and an all-solid lithium secondary battery including the same.
또한, 본 발명에 따른 전고체 리튬 이차전지용 양극 활물질의 제조방법을 제공하고자 한다.In addition, an object of the present invention is to provide a method of manufacturing a cathode active material for an all-solid-state lithium secondary battery.
본 발명은 상기 과제를 해결하기 위하여, 하기 [화학식 1]로 표시되는 산화물 및 상기 산화물 입자의 표면을 둘러싸면서 형성된 리튬 화합물 코팅층을 포함하는 전고체 리튬 이차전지용 양극 활물질을 제공한다.The present invention provides an anode active material for an all-solid-state lithium secondary battery comprising an oxide represented by the following [Formula 1] and a lithium compound coating layer formed while surrounding the surface of the oxide particles.
[화학식 1][Formula 1]
Li1+X(M)O2 Li 1 + X (M) O 2
상기 [화학식 1]에서, In [Formula 1],
M은 Co, Mn 또는 Ni을 포함한 전이 금속 또는 이들의 혼합물이고, x는 0 < x < 1이고, 바람직하게는 0.10 < x < 0.20이다.M is a transition metal comprising Co, Mn or Ni or mixtures thereof, x is 0 <x <1, preferably 0.10 <x <0.20.
또한, 상기 리튬 화합물 코팅층은 리튬하이드록사이드(LiOH)를 포함한 리튬염 및 리튬카보네이트(Li2CO3)와 같은 리튬 화합물 중에서 선택된 1종 이상으로 이루어진 것을 특징으로 한다.In addition, the lithium compound coating layer is characterized by consisting of at least one selected from lithium compounds, such as lithium salts including lithium hydroxide (LiOH) and lithium carbonate (Li 2 CO 3 ).
또한, 본 발명은 황화물계 고체 전해질과 상기 본 발명에 따른 양극 활물질을 포함하는 전극을 포함하는 전고체 리튬 이차전지를 제공한다.In addition, the present invention provides an all-solid-state lithium secondary battery comprising a sulfide-based solid electrolyte and an electrode including the cathode active material according to the present invention.
또한, 본 발명은 활물질 합성 공정에서 동시에 리튬 화합물 코팅층을 형성할 수도 있고, 합성되어 있는 활물질에 2차 공정을 통해 리튬 화합물 코팅층을 형성시킬 수 있는 양극 활물질의 제조방법을 제공하여, 표면에 코팅층이 없는 활물질에 비하여 전지 구성시 활물질의 전이금속 원소의 확산으로 인한 저항층 형성 또는 포텐셜 차이로 인한 리튬 결핍층 형성을 억제시키고 활물질과 전해질의 향상된 접촉면적으로 인한 넓은 리튬이온의 확산 경로를 갖출 수 있는 양극 활물질을 제공한다.In addition, the present invention may form a lithium compound coating layer at the same time in the active material synthesis process, and provides a method for producing a positive electrode active material that can form a lithium compound coating layer through the secondary process to the active material synthesized, the coating layer is on the surface Compared with the active material, it can suppress the formation of the resistive layer due to the diffusion of the transition metal element of the active material or the formation of the lithium deficiency layer due to the potential difference, and have a wider diffusion path of lithium ions due to the improved contact area between the active material and the electrolyte. It provides a positive electrode active material.
본 발명에 따른 양극 활물질의 제조방법은 각각 하기 단계를 포함하는 것을 특징로 한다.Method for producing a positive electrode active material according to the invention is characterized in that it comprises the following steps, respectively.
(a) 리튬 전구체와 금속염을 1.10 : 1 내지 1.50 : 1의 몰비로 증류수에 용해 후 혼합하여 혼합용액을 수득하는 단계,(a) dissolving a lithium precursor and a metal salt in distilled water at a molar ratio of 1.10: 1 to 1.50: 1 to obtain a mixed solution by mixing;
(b) 상기 혼합용액을 가열하고, 교반하여 용매를 증발시키면서 건조하는 단계,(b) heating the mixed solution and stirring to dry the solvent while evaporating;
(c) 상기 건조 단계 이후 600-1000 ℃에서 열처리하는 단계.(c) heat treatment at 600-1000 ° C. after the drying step.
이에 의해서 제조되는 전고체 리튬 이차전지용 양극 활물질의 표면은 리튬 화합물 코팅층으로 둘러싸여 있으며, 상기 리튬 화합물 코팅층은 상기 양극 활물질의 합성과 동시에 표면에 형성되는 것을 특징으로 한다.The surface of the cathode active material for an all-solid-state lithium secondary battery manufactured by this is surrounded by a lithium compound coating layer, and the lithium compound coating layer is formed on the surface simultaneously with the synthesis of the cathode active material.
본 발명의 일 실시예에 의하면, 상기 리튬 전구체는 리튬나이트레이트, 리튬하이드록사이드, 리튬시트레이트, 리튬아세테이트, 리튬설페이트 및 리튬카보네이트 중에서 선택될 수 있으며, 상기 금속염은 Co, Ni 또는 Mn을 포함하는 전이금속의 질산염, 아세트산염 또는 시트르산염 중에서 선택되는 1종 이상일 수 있다.According to one embodiment of the invention, the lithium precursor may be selected from lithium nitrate, lithium hydroxide, lithium citrate, lithium acetate, lithium sulfate and lithium carbonate, the metal salt includes Co, Ni or Mn It may be at least one selected from nitrate, acetate or citrate of the transition metal.
본 발명의 일 실시예에 의하면, 상기 (b) 단계는 40-250 ℃ 온도로 가열하여 수행될 수 있다.According to an embodiment of the present invention, step (b) may be performed by heating to a temperature of 40-250 ℃.
본 발명의 일 실시예에 의하면, 상기 리튬 화합물 코팅층은 리튬하이드록사이드(LiOH)을 포함한 리튬염 및 리튬카보네이트(Li2CO3)와 같은 리튬 화합물 중에서 선택된 1종 이상으로 이루어질 수 있으며, 바람직하게, 상기 리튬 화합물 코팅층은 리튬카보네이트(Li2CO3)일 수 있으며, 상기 리튬카보네이트는 상기 (c) 단계의 열처리가 탄산가스(CO2) 또는 탄산가스를 포함한 복합 가스 분위기 분위기에 수행되는 경우에 형성된 것일 수 있다.According to one embodiment of the present invention, the lithium compound coating layer may be made of at least one selected from lithium compounds such as lithium salts including lithium hydroxide (LiOH) and lithium carbonate (Li 2 CO 3 ), preferably The lithium compound coating layer may be lithium carbonate (Li 2 CO 3 ), and the lithium carbonate may be used when the heat treatment of step (c) is performed in a complex gas atmosphere including carbon dioxide (CO 2 ) or carbon dioxide. It may be formed.
또한, 본 발명에 따른 합성되어 있는 활물질에 2차 공정을 통해 리튬 화합물 코팅층을 형성시킬 수 있는 양극 활물질의 제조방법은 하기 단계를 포함한다.In addition, the method of manufacturing a cathode active material capable of forming a lithium compound coating layer through a secondary process on the active material synthesized according to the present invention includes the following steps.
(a) 리튬 전구체를 물에 용해하고 교반하여 리튬 전구체 용액을 수득하는 단계,(a) dissolving a lithium precursor in water and stirring to obtain a lithium precursor solution,
(b) 상기 리튬 전구체 용액에 하기 [화학식 1]로 표시되는 산화물 활물질을 분산시켜 혼합 용액을 수득하는 단계,(b) dispersing an oxide active material represented by the following [Formula 1] in the lithium precursor solution to obtain a mixed solution,
(c) 상기 혼합용액을 건조 후, 600-1000 ℃에서 열처리하는 단계.(c) after drying the mixed solution, heat treatment at 600-1000 ℃.
상기 산화물 활물질의 표면은 리튬 화합물 코팅층을 둘러싸여 있는 것을 특징으로 한다.The surface of the oxide active material is characterized by surrounding the lithium compound coating layer.
[화학식 1][Formula 1]
Li1+X(M)O2 Li 1 + X (M) O 2
상기 [화학식 1]에서, M은 Co, Mn 또는 Ni을 포함한 전이금속 또는 이들의 혼합물이고, X는 0 < X < 1이다.In Formula 1, M is a transition metal including Co, Mn, or Ni, or a mixture thereof, and X is 0 <X <1.
본 발명의 일 실시예에 의하면, 상기 리튬 전구체는 리튬나이트레이트, 리튬하이드록사이드, 리튬시트레이트, 리튬아세테이트, 리튬설페이트 및 리튬카보네이트 중에서 선택될 수 있으며, 상기 리튬 화합물 코팅층은 상기 리튬 화합물 코팅층은 리튬하이드록사이드(LiOH)을 포함한 리튬염 및 리튬카보네이트(Li2CO3)와 같은 리튬 화합물 중에서 선택된 1종 이상으로 이루어질 수 있다.According to one embodiment of the invention, the lithium precursor may be selected from lithium nitrate, lithium hydroxide, lithium citrate, lithium acetate, lithium sulfate and lithium carbonate, the lithium compound coating layer is the lithium compound coating layer It may be made of one or more selected from lithium compounds such as lithium salts including lithium hydroxide (LiOH) and lithium carbonate (Li 2 CO 3 ).
본 발명에 따른 전고체 리튬 이차전지의 양극 활물질은 리튬 화합물로 이루어진 코팅층이 입자 표면을 둘러싸면서 형성되어 있는 것을 특징으로 하고, 이러한 코팅층이 황화물계 고체 전해질과 전극의 계면반응을 억제해주는 기능층으로 작용하여 전지 특성을 크게 향상시킬 수 있다.The positive electrode active material of the all-solid-state lithium secondary battery according to the present invention is characterized in that the coating layer made of a lithium compound is formed surrounding the particle surface, the coating layer is a functional layer to suppress the interfacial reaction between the sulfide-based solid electrolyte and the electrode Can significantly improve battery characteristics.
또한, 본 발명에 따른 양극 활물질은 활물질 합성 공정에서 동시에 리튬 화합물 코팅층이 형성되거나 합성되어 있는 활물질에 2차 공정을 통해 리튬 화합물 코팅층을 형성시킴으로써 표면에 코팅층이 없는 활물질에 비하여 전지 구성시 충방전 과정 중 발생하는 활물질의 전이금속 원소의 확산으로 인한 저항층 형성 또는 포텐셜 차이로 인한 리튬 결핍층 형성을 억제시키고 활물질과 전해질의 향상된 접촉면적으로 인한 넓은 리튬이온의 확산 경로를 갖출 수 있다.In addition, the positive electrode active material according to the present invention is a charge and discharge process when the battery composition compared to the active material without a coating layer on the surface by forming a lithium compound coating layer on the active material in which the lithium compound coating layer is simultaneously formed or synthesized in the active material synthesis process through a secondary process It can suppress the formation of the resistive layer due to the diffusion of the transition metal element of the active material, or the formation of a lithium deficient layer due to the potential difference, and can have a wide diffusion path of lithium ions due to the improved contact area between the active material and the electrolyte.
또한, 본 발명에 따른 양극 활물질의 제조방법 중의 일 실시예에 따르면, 활물질 합성공정에서 동시에 코팅층이 형성되는 것을 특징으로 하여 계면 반응 억제를 위한 코팅층 형성 후공정이 별도로 요구되지 않아 생산 공정 단축할 수 있는 장점도 갖는다.In addition, according to one embodiment of the method for manufacturing a positive electrode active material according to the present invention, the coating layer is formed at the same time in the active material synthesis process, the post-layer coating process for inhibiting the interfacial reaction is not required separately can shorten the production process It also has the advantage.
도 1은 본 발명의 합성예 1과 4에 따라 각각 합성된 리튬 화합물(Li2CO3)이 코팅된 리튬 코발트 산화물 활물질에 대한 SEM 이미지(도 1의 ⓑ(In-situ), ⓓ(Ex-situ)로서, 표면이 코팅되지 않은 리튬 코발트 산화물 활물질(도 1의 ⓐ, ⓒ)의 SEM 이미지와 비교한 이미지이다. 1 is a SEM image of a lithium cobalt oxide active material coated with a lithium compound (Li 2 CO 3 ) synthesized according to Synthesis Examples 1 and 4 of the present invention, respectively (ⓑ (In-situ), ⓓ (Ex- situ), which is an image compared with an SEM image of a lithium cobalt oxide active material (ⓐ, ⓒ in FIG. 1) with no surface coated.
도 2는 본 발명의 합성예 1과 4에 따라 각각 후처리 없이(in-situ) 리튬 화합물을 표면에 코팅한 경우와 후처리를 통해(ex-situ) 리튬 화합물을 코팅한 경우를 코팅 전 시료와 함께 결정구조를 비교한 XRD 그래프이다.2 is a sample before coating the case in which the lithium compound is coated on the surface and the after-treatment (ex-situ), respectively, according to the synthesis examples 1 and 4 of the present invention without the after-treatment (in-situ) XRD graph comparing the crystal structure with.
도 3은 본 발명의 합성예 1과 4에 따라 각각 후처리 없이(in-situ) 리튬 화합물을 표면에 코팅한 경우와 후처리를 통해(ex-situ) 리튬 화합물을 코팅한 경우를 코팅 전 시료와 함께 IR 분광법으로 구조를 분석 및 비교한 그래프이다.3 is a sample before coating the case in which the lithium compound is coated on the surface and the after-treatment (ex-situ) when the lithium compound is coated on the surface according to Synthesis Examples 1 and 4 of the present invention, respectively. And a graph of the structure analysis and comparison by IR spectroscopy.
도 4는 본 발명의 합성예 1에서 리튬 전구체의 리튬 전구체의 양을 각각 10 wt%, 20 wt%, 30 wt%로 조절하여 합성한 리튬 코발트 산화물 활물질들에 대한 전고체 전지의 충방전 곡선을 나타내는 그래프이다.FIG. 4 shows charge and discharge curves of an all-solid-state battery for lithium cobalt oxide active materials synthesized by adjusting the amounts of lithium precursors of lithium precursors in Synthesis Example 1 to 10 wt%, 20 wt%, and 30 wt%, respectively. It is a graph.
도 5는 본 발명의 합성예 1에서 리튬과 코발트의 비율을 1.2 : 1로 합성한 리튬 화합물이 코팅된 활물질과 표면에 코팅이 되어있지 않은 리튬 코발트 산화물 활물질에 대한 전고체 전지의 전기화학적 충방전 곡선을 나타내는 그래프이다.5 is an electrochemical charge and discharge of an all-solid-state battery for a lithium cobalt oxide active material coated with a lithium compound coated with a lithium compound having a ratio of 1.2: 1 to lithium and cobalt in a synthesis example 1 of the present invention. A graph showing a curve.
도 6은 본 발명의 합성예 1에 따라 리튬의 비율을 달리하여 리튬 화합물이 코팅된 리튬 코발트 산화물 활물질에 대한 전고체 전지의 충방전 수명특성을 비교하여 나타내는 그래프이다.FIG. 6 is a graph showing charge and discharge life characteristics of an all-solid-state battery with respect to a lithium cobalt oxide active material coated with a lithium compound by varying the proportion of lithium according to Synthesis Example 1 of the present invention.
도 7은 본 발명의 합성예 2에 따라 다양한 전구체들을 이용하여 합성된 리튬 코발트 산화물 활물질들에 대한 전고체 전지의 전기화학적 충방전 곡선을 나타내는 그래프이다.7 is a graph showing an electrochemical charge and discharge curve of an all-solid-state battery for lithium cobalt oxide active materials synthesized using various precursors according to Synthesis Example 2 of the present invention.
도 8은 본 발명의 합성예 3에 따라 합성된 리튬 니켈 코발트 산화물 활물질과 표면에 코팅이 되어있지 않은 리튬 니켈 코발트 산화물 활물질에 대한 전고체 전지의 충방전 곡선을 나타내는 그래프이다.8 is a graph showing charge and discharge curves of an all-solid-state battery for a lithium nickel cobalt oxide active material synthesized according to Synthesis Example 3 of the present invention and a lithium nickel cobalt oxide active material not coated on its surface.
도 9는 본 발명의 합성예 4에 따라 상용 리튬 코발트 산화물에 다양한 전구체를 사용하여 표면에 리튬 화합물을 코팅한 활물질들과 표면에 코팅이 되어있지 않은 상용 리튬 코발트 산화물 활물질에 대한 전고체 전지의 충방전 곡선을 나타내는 그래프이다.FIG. 9 is a charge of an all-solid-state battery for active materials coated with a lithium compound on a surface using various precursors to commercial lithium cobalt oxide and a commercial lithium cobalt oxide active material not coated on the surface according to Synthesis Example 4 of the present invention. It is a graph showing a discharge curve.
도 10은 본 발명의 합성예 4 에 따라 상용 리튬 코발트 산화물에 다양한 전구체를 사용하여 표면에 리튬 화합물을 코팅한 활물질들과 표면에 코팅이 되어있지 않은 상용 리튬 코발트 산화물 활물질에 대한 전고체 전지의 충방전 속도를 달리했을 때의 용량 특성을 나타내는 그래프이다.FIG. 10 is a charge of an all-solid-state battery for active materials coated with a lithium compound on the surface using various precursors to commercial lithium cobalt oxide and a commercial lithium cobalt oxide active material not coated on the surface according to Synthesis Example 4 of the present invention. It is a graph showing capacity characteristics when the discharge rate is changed.
도 11은 본 발명의 합성예 5에 따라 상용 리튬 니켈-코발트-망간(6:2:2) 산화물 표면에 리튬 화합물을 코팅한 활물질과 코팅하지 않은 상용 리튬 니켈-코발트-망간(6:2:2) 산화물 활물질에 대한 전고체 전지의 충방전 곡선을 나타내는 그래프이다.11 is a commercial lithium nickel-cobalt-manganese (6: 2: 2) active material coated with a lithium compound on the surface of a commercially available lithium nickel-cobalt-manganese (6: 2: 2) according to Synthesis Example 5 of the present invention. 2) A graph showing charge and discharge curves of an all-solid-state battery with respect to the oxide active material.
도 12는 본 발명의 합성예 5에 따라 상용 리튬 니켈-코발트-망간(6:2:2) 산화물 표면에 리튬 화합물을 코팅한 활물질과 코팅하지 않은 상용 리튬 니켈-코발트-망간(6:2:2) 산화물 활물질에 대한 전고체 전지의 충방전 수명특성을 나타내는 그래프이다.12 is a commercial lithium nickel-cobalt-manganese (6: 2: 2) active material coated with a lithium compound on the surface of a commercially available lithium nickel-cobalt-manganese (6: 2: 2) oxide according to Synthesis Example 5 of the present invention. 2) A graph showing charge and discharge life characteristics of an all-solid-state battery with respect to an oxide active material.
이하, 본 발명을 더욱 상세하게 설명한다.Hereinafter, the present invention will be described in more detail.
본 발명은 리튬 화합물로 표면 처리되어 있는 산화물 활물질과 그 제조방법 및 이를 채용하여 고체 전해질에서의 계면 반응을 효과적으로 억제할 수 있는 전고체 리튬 이차전지에 관한 것이다.The present invention relates to an oxide active material surface-treated with a lithium compound, a method for producing the same, and an all-solid-state lithium secondary battery capable of effectively suppressing an interfacial reaction in a solid electrolyte by employing the same.
본 발명에 따른 양극 활물질을 포함하는 전극 및 황화물계 고체 전해질을 포함하는 전고체 리튬 이차전지에서, 본 발명에 따른 양극 활물질은 리튬 화합물로 이루어진 코팅층이 입자 표면을 둘러싸면서 형성되어 있어 황화물계 고체 전해질과 전극의 계면반응을 억제해주는 코팅 기능층으로 작용하여 전지 특성을 크게 향상시킬 수 있다.In an all-solid-state lithium secondary battery comprising an electrode including a positive electrode active material and a sulfide-based solid electrolyte according to the present invention, the positive electrode active material according to the present invention is formed with a coating layer made of a lithium compound surrounding the particle surface to form a sulfide-based solid electrolyte. By acting as a coating function layer that suppresses the interfacial reaction between the electrode and the electrode can significantly improve the battery characteristics.
종래 액체 전해질을 사용한 리튬 이차전지 시스템에서는 활물질 제조 공정 중 표면에 생성되는 리튬카보네이트와 같은 이차상 또는 불순물이 충방전 과정에서 액체 전해질과 부반응을 일으켜 전지 특성을 저하시키기 때문에 합성 후 세척 또는 고온의 열처리를 통해 불순물의 양을 최소화시키려고 하고 있다.In the conventional lithium secondary battery system using a liquid electrolyte, secondary phase or impurities such as lithium carbonate generated on the surface of the active material manufacturing process side reaction with the liquid electrolyte during the charge and discharge process to degrade the battery characteristics, so washing or high temperature heat treatment after synthesis To minimize the amount of impurities.
하지만, 본 발명에서는 제조과정에서 리튬 소스를 과량 첨가하여 합성 후 잔류하는 리튬 소스에 의해 활물질 표면에 불순물로 이루어진 코팅층을 의도적으로 형성시켜서 액체 전해질 시스템에서와는 달리 황화물계 고체 전해질과의 계면반응을 억제해주는 코팅 기능층으로 작용하도록 한 것을 특징으로 한다.However, in the present invention, an excessive amount of lithium source is added during the manufacturing process to intentionally form a coating layer of impurities on the surface of the active material by the lithium source remaining after synthesis, thereby inhibiting the interfacial reaction with the sulfide-based solid electrolyte unlike the liquid electrolyte system. It is characterized in that it serves as a coating functional layer.
또한, 합성과 동시에 리튬 화합물을 코팅하는 경우에는 용매에 리튬염 및 전이금속 염을 교반을 통해 용해하여 용액을 만들고 이를 건조 및 열처리를 통해 제조하며, 제조된 활물질은 리튬을 흡장 및 방출할 수 있는 구조를 갖는 입자 표면에 합성 후 잔류하는 과량의 리튬염으로부터 생성되는 혼합물이 표면에 코팅되어 코팅층을 이루는 형태를 갖는다.In addition, in the case of coating the lithium compound at the same time with the synthesis to dissolve the lithium salt and transition metal salt in a solvent to make a solution and to prepare it by drying and heat treatment, the prepared active material can occlude and release lithium The mixture resulting from the excess lithium salt remaining after synthesis on the surface of the particle having a structure is coated on the surface to form a coating layer.
또한, 이미 합성된 활물질에 리튬 화합물을 코팅하는 경우, 용매에 활물질과 리튬염을 교반을 통해 용해하고 이를 건조 및 열처리를 통해 제조하며, 제조된 활물질은 리튬을 흡장 및 방출할 수 있는 구조를 갖는 입자 표면에 합성 후 잔류하는 과량의 리튬 염으로부터 생성되는 혼합물이 표면에 코팅되어 코팅층을 이루는 형태를 갖는다.In addition, in the case of coating the lithium compound on the already synthesized active material, the active material and the lithium salt are dissolved in a solvent by stirring and drying and heat-treating them, and the prepared active material has a structure capable of occluding and releasing lithium. The mixture resulting from the excess lithium salt remaining after synthesis on the particle surface is coated on the surface to form a coating layer.
따라서, 전고체 리튬 이차전지에서, 본 발명에 따른 활물질의 표면에 생성되는 리튬 화합물 코팅층에 의해서 황화물계 고체 전해질과의 계면반응이 억제되어 전지 구성시 활물질의 전이금속 원소의 확산으로 인한 저항층 형성 또는 포텐셜 차이로 인한 리튬 결핍층 형성을 억제시키고 활물질과 전해질의 향상된 접촉면적으로 인한 넓은 리튬이온의 확산 경로를 가질 수 있다.Therefore, in the all-solid lithium secondary battery, the interfacial reaction with the sulfide-based solid electrolyte is suppressed by the lithium compound coating layer formed on the surface of the active material according to the present invention, thereby forming a resistance layer due to diffusion of the transition metal element of the active material during battery construction. Alternatively, the lithium deficiency layer may be suppressed due to the potential difference and may have a broad diffusion path of lithium ions due to the improved contact area between the active material and the electrolyte.
본 발명의 일 측면은 황화물계 고체 전해질을 이용하는 전고체 리튬 이차전지에서 전극과 황화물계 고체 전해질 간의 계면반응을 억제하여 우수한 사이클 및 율속 특성을 구현하여 전지 특성을 향상시킬 수 있는 전고체 리튬 이차전지용 활물질로서, 하기 [화학식 1]로 표시되는 산화물 및 상기 산화물 입자의 표면을 둘러싸면서 형성된 리튬 화합물 코팅층을 포함하는 것을 특징으로 한다.One aspect of the present invention is the all-solid lithium secondary battery using a sulfide-based solid electrolyte for all-solid lithium secondary battery that can improve the battery characteristics by inhibiting the interfacial reaction between the electrode and the sulfide-based solid electrolyte to implement excellent cycle and rate characteristics An active material includes an oxide represented by the following [Formula 1] and a lithium compound coating layer formed while surrounding the surface of the oxide particles.
[화학식 1][Formula 1]
Li1+X(M)O2 Li 1 + X (M) O 2
상기 [화학식 1]에서, M은 Co, Mn 또는 Ni을 포함한 전이금속 또는 이들의 혼합물이고, X는 0 < X < 1이고, 바람직하게는 0.10 < X < 0.20이다.In [Formula 1], M is a transition metal including Co, Mn or Ni or a mixture thereof, X is 0 <X <1, preferably 0.10 <X <0.20.
또한, 상기 리튬 화합물 코팅층은 리튬하이드록사이드(LiOH)을 포함한 리튬염 및 리튬카보네이트(Li2CO3)와 같은 리튬 화합물 중에서 선택된 1종 이상으로 이루어진 것을 특징으로 하며, 상기 코팅층을 이루는 일 물질에 해당하는 리튬염은 리튬나이트레이트, 리튬하이드록사이드, 리튬시트레이트, 리튬아세테이트, 리튬설페이트 및 리튬카보네이트 중에서 선택될 수 있다.In addition, the lithium compound coating layer is characterized in that it is made of at least one selected from lithium compounds, such as lithium salts including lithium hydroxide (LiOH) and lithium carbonate (Li 2 CO 3 ), in one material constituting the coating layer Corresponding lithium salts may be selected from lithium nitrate, lithium hydroxide, lithium citrate, lithium acetate, lithium sulfate and lithium carbonate.
본 발명의 다른 측면은 상기와 같은 조성, 구조 및 특징을 갖는 전고체 리튬 이차전지용 활물질의 제조방법에 관한 것이다.Another aspect of the present invention relates to a method for producing an active material for an all-solid-state lithium secondary battery having the composition, structure, and characteristics as described above.
합성과 동시에 리튬 화합물을 코팅하는 방법에서는, 용매에 리튬염 및 전이금속 염을 교반을 통해 용해하여 용액을 만들고 이를 건조 및 열처리를 통해 제조하며, 제조된 활물질은 리튬을 흡장 및 방출할 수 있는 구조를 갖는 입자 표면에 합성 후 잔류하는 과량의 리튬염으로부터 생성되는 혼합물이 표면에 피복되어 코팅층을 이루는 형태를 갖는다.In the method of coating the lithium compound at the same time with the synthesis, a lithium salt and a transition metal salt is dissolved in a solvent by stirring to prepare a solution, which is prepared by drying and heat treatment, and the prepared active material has a structure capable of occluding and releasing lithium The mixture produced from the excess lithium salt remaining after synthesis on the surface of the particles having a has a form to coat the surface to form a coating layer.
또한, 이미 합성된 활물질에 리튬 화합물을 코팅하는 방법에서는, 용매에 활물질과 리튬염을 교반을 통해 용해하고 이를 건조 및 열처리를 통해 제조하며, 제조된 활물질은 리튬을 흡장 및 방출할 수 있는 구조를 갖는 입자 표면에 합성 후 잔류하는 과량의 리튬 염으로부터 생성되는 혼합물이 표면에 코팅되어 코팅층을 이루는 형태를 갖는다.In addition, in the method for coating a lithium compound on the already synthesized active material, the active material and the lithium salt are dissolved in a solvent by stirring, and then manufactured by drying and heat treatment, and the prepared active material has a structure capable of occluding and releasing lithium. The mixture produced from the excess lithium salt remaining after synthesis on the surface of the particles having the form is coated on the surface to form a coating layer.
상기 리튬염의 종류는 특별히 제한되지 않고, 리튬나이트레이트, 리튬하이드록사이드, 리튬시트레이트, 리튬아세테이트, 리튬설페이트 및 리튬카보네이트 중에서 선택될 수 있고, 전이금속 염의 종류 역시 특별히 제한되지 않고, 구현하고자 하는 전지의 전압과 용량에 따라 Co, Ni, Mn 등의 전이금속을 포함하는 염을 하나 또는 그 이상을 혼합하여 적용하여 가능하다.The type of the lithium salt is not particularly limited, and may be selected from lithium nitrate, lithium hydroxide, lithium citrate, lithium acetate, lithium sulfate, and lithium carbonate, and the type of transition metal salt is not particularly limited and is intended to be implemented. Depending on the voltage and capacity of the battery, it is possible to apply a mixture containing one or more salts containing transition metals such as Co, Ni and Mn.
또한, 여기에서 리튬염 및 전이금속염의 혼합 용액 제조에 있어서 리튬염 용액과 전이금속염 용액을 개별적으로 제조하고 리튬염 용액에 전이금속염 용액을 조금씩 첨가하거나, 전이금속염 용액에 리튬염 용액을 조금씩 첨가할 수 있으며, 또한 하나의 용매에 리튬염과 전이금속염을 동시에 녹여 제조할 수 있다.Further, in preparing a mixed solution of lithium salt and transition metal salt, a lithium salt solution and a transition metal salt solution may be prepared separately, and a transition metal salt solution may be added little by little to the lithium salt solution, or a lithium salt solution may be added little by little to the transition metal salt solution. It can also be prepared by dissolving lithium salt and transition metal salt in one solvent at the same time.
본 발명에서는 활물질 제조를 전구체 용액을 기반으로 한 방법을 택하고 있지만 이는 본 발명의 일 실시예일 뿐 고상법 등 다양한 합성 방법을 이용해 다른 출발 물질로부터 합성하여도 상관없으며 리튬을 과량 첨가하여 표면에 부산물을 형성할 수 있는 방법이라면 크게 한정하지 않는다.In the present invention, the method of preparing the active material is selected based on the precursor solution, but this is only one embodiment of the present invention and may be synthesized from other starting materials using various synthetic methods such as solid phase method, and by-products are added to the surface by adding excessive lithium. If it is a method that can form a not limited.
제조된 활물질 표면에 과량의 리튬 소스로부터 생성된 부산물의 코팅 정도는 리튬 소스의 첨가량에 의해 조절된다.The degree of coating of by-products generated from the excess lithium source on the surface of the prepared active material is controlled by the amount of lithium source added.
리튬 소스의 첨가량은 Li/Co의 비율이 1.0 내지 1.5가 되도록 하며, 리튬 교반 시간 및 온도는 염이 충분히 균일하게 용해된 후 용매를 증발시킬 수 있는 조건 내에서 크게 제한하지 않는다.The addition amount of the lithium source is such that the ratio of Li / Co is 1.0 to 1.5, and the lithium agitation time and temperature are not greatly limited within the conditions in which the solvent can be evaporated after the salt is sufficiently uniformly dissolved.
또한, 교반 후에 용매가 충분히 제거될 수 있도록 40 ℃ 이상에서 건조 과정을 거치며 이후 층상 구조의 높은 결정성을 갖는 활물질 제조를 위해 600 내지 1000 ℃의 온도에서 후열처리 공정을 거친다. 열처리 온도 및 시간은 원하는 결정화도 및 입자크기에 따라 자유롭게 조절가능하다.In addition, after stirring, the solvent is dried at 40 ° C. or higher to sufficiently remove the solvent, and then subjected to a post-heat treatment process at a temperature of 600 to 1000 ° C. to prepare an active material having a high crystallinity of a layered structure. The heat treatment temperature and time are freely adjustable according to the desired crystallinity and particle size.
또한, 본 발명의 또 다른 측면은 상기 전고체 리튬 이차전지용 활물질과 황화물계 고체 전해질을 포함하는 전고체 리튬 이차전지에 관한 것이다.In addition, another aspect of the present invention relates to an all-solid lithium secondary battery comprising the active material for the all-solid lithium secondary battery and a sulfide-based solid electrolyte.
본 발명에 따른 활물질과 황화물계 고체 전해질을 혼합하여 복합전극으로 제조하고, 전자 전도성을 향상시키기 위해 도전제를 첨가할 수 있다. 이러한 복합전극 제조를 위한 혼합 방법은 고체 전해질, 활물질 및 도전제를 건식 또는 습식 방법에 의해 실시 가능하며 구성 입자들 사이에 균일한 분포를 이루고 입자 사이에 컨택을 향상시킬 수 있는 방법이면 크게 한정하지 않는다.The active material according to the present invention and a sulfide-based solid electrolyte may be mixed to prepare a composite electrode, and a conductive agent may be added to improve electronic conductivity. The mixing method for manufacturing the composite electrode may be performed by a dry or wet method of the solid electrolyte, the active material, and the conductive agent, and the method of forming a uniform distribution among the constituent particles and improving the contact between the particles is not particularly limited. Do not.
복합 전극의 형태는 목적에 따라 분말 형태로 고체 전해질 상단에 도포하거나 바인더를 첨가하여 Al, Cu, Ti, SUS 등과 금속 시트 표면 위에 코팅하여 시트 형태가 될 수도 있다.The shape of the composite electrode may be applied to the top of the solid electrolyte in the form of a powder or coated with Al, Cu, Ti, SUS, etc. on the surface of the metal sheet to form a sheet according to the purpose.
또한, 복합 전극에 제조에 사용되는 황화물계 고체 전해질은 망목수식체인 Li2S를 포함하며 망목형성체로 P2S5, B2S3, SiS2, GeS2 등과 같은 다양한 황화물계 분말을 사용할 수 있다.In addition, the sulfide-based solid electrolyte used in the manufacture of the composite electrode includes Li 2 S, which is a mesh tree, and various sulfide powders such as P 2 S 5 , B 2 S 3 , SiS 2 , and GeS 2 may be used as the network forming body. have.
고체 전해질은 크게 비정질계 및 결정질계 형태로 제조가 가능하다. 비정질계를 기반으로 한 고체 전해질 합성은 망목수식체와 망목형성체 분말을 화학량론비에 맞게 혼합한 후 용융-냉각법 또는 기계적 밀링법을 이용해 합성 및 비정질화를 시키며, 추후 선택적으로 전도도 향상을 위해 열처리 공정을 거친다. 결정질계 고체 전해질은 황화물계 분말들을 화학량론비에 맞게 혼합한 후 진공 또는 불활성 기체 분위기 하에서 고온 열처리를 통한 고상법을 통해 제조된다. 이렇게 만들어진 고체전해질은 전해질층에 사용되며, 활물질/도전제 및 바인더와 함께 혼합하여 복합전극 내 이온 전도 경로를 제공하는데 또한 사용된다.Solid electrolytes can be largely prepared in amorphous and crystalline forms. Solid electrolyte synthesis based on the amorphous system mixes the tree planting body and the tree forming powder to the stoichiometric ratio, and then synthesizes and amorphous by using melt-cooling method or mechanical milling method, and then heat treatment to selectively improve conductivity. Go through the process. The crystalline solid electrolyte is prepared through a solid phase method through high temperature heat treatment under a vacuum or inert gas atmosphere after the sulfide-based powders are mixed in a stoichiometric ratio. The solid electrolyte thus made is used in the electrolyte layer and also mixed with the active material / conductor and binder to provide an ion conducting path in the composite electrode.
이하, 바람직한 실시예를 들어 본 발명을 더욱 상세하게 설명한다. 그러나, 이들 실시예는 본 발명을 보다 구체적으로 설명하기 위한 것으로, 본 발명의 범위가 이에 의하여 제한되지 않고, 본 발명의 범주 및 기술사상 범위 내에서 다양한 변경 및 수정이 가능함은 당업계의 통상의 지식을 가진 자에게 자명할 것이다.Hereinafter, the present invention will be described in more detail with reference to preferred examples. However, these examples are intended to illustrate the present invention in more detail, and the scope of the present invention is not limited thereto, and various changes and modifications are possible within the scope and spirit of the present invention. It will be self-evident to those who have knowledge.
하기 합성예 1 내지 3은 산화물 활물질의 합성과 동시에 다양한 조성의 리튬 화합물이 표면에 코팅된 활물질을 합성하였다.Synthesis Examples 1 to 3 synthesized the active material coated on the surface of the lithium compound of various compositions simultaneously with the synthesis of the oxide active material.
합성예 1 : 다양한 조성의 리튬 화합물이 표면에 코팅된 활물질, 리튬 코발트 산화물(Li1+xCoO2)의 제조Synthesis Example 1 Preparation of Active Material and Lithium Cobalt Oxide (Li 1 + x CoO 2 ) Coated with Lithium Compounds of Various Compositions
Lithium nitrate(LiNO3)와 Cobalt nitrate hexahydrate(Co(NO3)2·6H2O)를 1.1 : 1 내지 1.3 : 1의 몰비로 물에 용해시킨 후 교반시키면서 물을 휘발시킨다. 완전히 물을 건조시킨 후 800 ℃에서 5시간 동안 대기에서 열처리 과정을 통해 합성하였다.Lithium nitrate (LiNO 3 ) and Cobalt nitrate hexahydrate (Co (NO 3 ) 2 .6H 2 O) are dissolved in water in a molar ratio of 1.1: 1 to 1.3: 1 and then volatilized while stirring. After completely drying the water was synthesized by heat treatment in the air for 5 hours at 800 ℃.
합성예 2 : 다양한 리튬 전구체를 이용하여 리튬 화합물이 표면에 코팅된 리튬 코발트 산화물(LiCoO2)의 제조Synthesis Example 2 Preparation of Lithium Cobalt Oxide (LiCoO 2 ) Coated with Lithium Compound on the Surface Using Various Lithium Precursors
상기 합성예 1에서 사용한 Lithium nitrate(LiNO3) 대신에 Lithium hydroxide(LiOH), Lithium acetate CH3COO-Li)를 사용한 것을 제외하고는 상기 합성예 1의 방법과 동일한 방법으로 합성하였다.Lithium hydroxide (LiOH), instead of Lithium nitrate (LiNO 3 ) used in Synthesis Example 1 was synthesized in the same manner as in Synthesis Example 1 except that Lithium hydroxide (LiOH), Lithium acetate CH 3 COO-Li.
합성예 3 : 리튬 코발트 산화물을 대체할 수 있는 리튬 니켈 코발트 산화물(LiNi0.02Co0.98O2)과 리튬 산화물이 표면에 코팅된 리튬 니켈 코발트 산화물(LiNi0.02Co0.98O2)의 제조Synthesis Example 3: Preparation of lithium-nickel-cobalt oxide to replace the lithium cobalt oxide (LiNi 0.02 Co 0.98 O 2) and lithium nickel oxide is a lithium cobalt oxide is coated on the surface (LiNi 0.02 Co 0.98 O 2)
Cobalt nitrate hexahydrate(Co(NO3)2·6H2O) 대신에 Nickel nitrate hexahydrate(Ni(NO3)2·6H2O)와 Cobalt nitrate hexahydrate(Co(NO3)2·6H2O)(0.02 : 0.98의 몰비)를 사용한 것을 제외하고는 상기 합성예 1의 방법과 동일한 방법으로 합성하였다. Cobalt nitrate hexahydrate (Co (NO 3 ) 2 · 6H 2 O) instead of the Nickel nitrate hexahydrate (Ni (NO 3 ) 2 · 6H 2 O) and Cobalt nitrate hexahydrate (Co (NO 3 ) 2 · 6H 2 O) (0.02 Synthesis was carried out in the same manner as in Synthesis Example 1, except that: a molar ratio of 0.98) was used.
하기 합성예 4 내지 5는 이미 합성되어 있는 산화물 활물질에 리튬 화합물을 코팅하여 다양한 조성의 리튬 화합물이 표면에 코팅된 활물질을 합성하였다.Synthesis Examples 4 to 5 below were coated with a lithium compound on the oxide active material is already synthesized to synthesize an active material coated on the surface of the lithium compound of various compositions.
합성예 4 : 이미 합성되어 있는 리튬 코발트 산화물 활물질에 리튬 화합물을 코팅Synthesis Example 4 Coating Lithium Compound on Lithium Cobalt Oxide Active Material
활물질 중량 대비 코팅량을 계산하여 리튬 전구체를 물에 용해시킨다. 1시간 정도 교반을 한 뒤에 활물질을 함께 약간의 열과 함께 분산시킨다. 완전히 건조 후, 600 ℃에서 5시간 동안 열처리를 진행하여 합성하였다.The lithium precursor is dissolved in water by calculating the coating amount based on the weight of the active material. After stirring for about 1 hour, the active materials are dispersed together with some heat. After drying completely, the mixture was heat-treated at 600 ° C. for 5 hours for synthesis.
합성예 5 : 이미 합성되어 있는 상용 리튬 니켈-코발트-망간 산화물 활물질(Li[Ni0.6Co0.2Mn0.2])O2) 표면에 코팅Synthesis Example 5 Coating on the surface of commercially available commercially available lithium nickel-cobalt-manganese oxide active material (Li [Ni 0.6 Co 0.2 Mn 0.2 ]) O 2 )
상기 합성예 4에서 리튬 코발트 산화물 활물질 대신에 리튬 니켈-코발트-망간 산화물 활물질로 사용한 것을 제외하고는 상기 합성예 4의 방법과 동일한 방법으로 진행하여 합성하였다.Synthesis was carried out in the same manner as in Synthesis Example 4, except that Synthesis Example 4 was used as a lithium nickel-cobalt-manganese oxide active material instead of the lithium cobalt oxide active material.
실시예 : 전고체 셀의 제조Example: Preparation of All Solid Cells
(1) 황화물계 고체 전해질의 제조(1) Preparation of Sulfide Solid Electrolyte
Li2S와 P2S5 분말을 지르코니아 밀링 포트 안에 넣고 기계적 밀링(MM: Mechanical Milling)을 실시하여 비정질 고체전해질을 합성하였다. 또한, 이온전도도 향상을 위해 200 내지 300 ℃ 아르곤 분위기 하에서 후속 열처리 공정을 통하여 글래스 세라믹(glass-ceramics) 분말을 제조하였다.Li 2 S and P 2 S 5 powder was put in a zirconia milling pot and subjected to mechanical milling (MM) to synthesize an amorphous solid electrolyte. In addition, glass-ceramics powders were prepared through a subsequent heat treatment process under an argon atmosphere of 200 to 300 ° C. to improve ion conductivity.
(2) 복합 전극의 제조(2) Preparation of Composite Electrode
아르곤 분위기의 글로브 박스 안에서 막자 사발을 이용하여 상기 제조된 황화물계 고체 전해질(78Li2S-22P2S5)과 상기 합성예 1 내지 5에 따라 합성된 양극 활물질 및 도전제(super P-carbon)를 질량비 58.8 : 39.2 : 2로 건식 혼합 후 고체 전해질과 반응성이 적은 헵탄 용매를 첨가하여 습식 혼합을 30분간 실시하였다. 캐스팅을 통해 시트 형태로 제조할 경우에는 바인더를 첨가한다. 제조된 복합전극은 금속, 탄소 섬유 시트와 같은 집전체 위에 도포하거나 셀 제조과정에서 전해질 표면에 도포하고 도포 후 100 ℃ 내지 200 ℃에서 건조 과정을 거친다.A sulfide-based solid electrolyte (78Li 2 S-22P 2 S 5 ) prepared by using a mortar and pestle in a glove box in an argon atmosphere, and a cathode active material and a conductive agent (super P-carbon) synthesized according to Synthesis Examples 1 to 5 above. Was dry mixed at a mass ratio of 58.8: 39.2: 2, and then wet mixing was performed for 30 minutes by adding a heptan solvent having a low reactivity to the solid electrolyte. In the case of manufacturing a sheet through casting, a binder is added. The manufactured composite electrode is coated on a current collector such as a metal or carbon fiber sheet or coated on an electrolyte surface in a cell manufacturing process and then dried at 100 ° C. to 200 ° C. after application.
(3) 벌크 셀 제조(3) bulk cell manufacturing
물성 평가를 위한 벌크 셀 제조를 위해 황화물계 고체전해질을 성형 몰드 내에서 1 톤으로 가압하여 얇은 전해질 층을 형성하고 그 위에 복합전극과 탄소 섬유 시트 집전체를 순차적으로 부착하여 4 톤으로 가압한다. 이후 상대전극으로 인듐 호일을 반대편에 부착 후 다시 3 톤으로 가압하여 벌크 셀을 제작하였다. 제작된 펠릿은 직경이 16 mm인 원형이며, 전지 평가를 위해 2032 SUS 코인 셀로 조립하였다.In order to prepare a bulk cell for evaluation of physical properties, the sulfide-based solid electrolyte is pressurized to 1 ton in a molding mold to form a thin electrolyte layer, and the composite electrode and the carbon fiber sheet current collector are sequentially attached thereto and pressurized to 4 tons. Thereafter, the indium foil was attached to the opposite side using the counter electrode and pressurized again to 3 tons to produce a bulk cell. The prepared pellets were circular with a diameter of 16 mm, and assembled into a 2032 SUS coin cell for battery evaluation.
실험예 1Experimental Example 1
상기 합성예 1과 4에 따라 합성한 표면에 리튬 화합물이 코팅된 리튬 코발트 산화물의 표면 상태를 비교하였다.The surface state of lithium cobalt oxide coated with a lithium compound on the surface synthesized according to Synthesis Examples 1 and 4 was compared.
도 1은 본 발명의 합성예 1과 4에 따라 각각 합성된 리튬 화합물(Li2CO3)이 코팅된 리튬 코발트 산화물 활물질에 대한 SEM 이미지(도 1의 ⓑ(in-situ), ⓓ(ex-situ)로서, 표면이 코팅되지 않은 리튬 코발트 산화물 활물질(도 1의 ⓐ, ⓒ)의 SEM 이미지와 비교한 이미지이다.1 is a SEM image of a lithium cobalt oxide active material coated with a lithium compound (Li 2 CO 3 ) synthesized according to Synthesis Examples 1 and 4 of the present invention, respectively (ⓑ (in-situ), ⓓ (ex- situ), which is an image compared with an SEM image of a lithium cobalt oxide active material (ⓐ, ⓒ in FIG. 1) with no surface coated.
도 1의 ⓐ는 합성 후 표면에 리튬 산화물 코팅층이 남아 있지 않도록 세척한 상태, ⓑ는 합성 후 표면에 리튬 산화물 코팅층이 생성된 상태, ⓒ는 상용 리튬 코발트 산화물, ⓓ는 상용 리튬 코발트 산화물의 표면에 후처리로 코팅층을 만든 상태의 리튬 코발트 산화물 활물질을 나타내고 있다.1 is a state in which the lithium oxide coating layer is left on the surface after synthesis, ⓑ is a state where a lithium oxide coating layer is formed on the surface after synthesis, ⓒ is a commercial lithium cobalt oxide, ⓓ is a surface of a commercial lithium cobalt oxide The lithium cobalt oxide active material in a state in which a coating layer is formed by post-treatment is shown.
후처리 없이 합성 과정(in-situ)에서 리튬 화합물을 코팅하게 되면(도 1의 ⓑ), 합성 후 세척한 상태(도 1의 ⓐ)에 코팅 이후에 비해 리튬화합물 형성으로 인한 입자들이 표면에 분포되어 거칠어진 것을 볼 수 있다.If the lithium compound is coated in the synthesis process (in-situ) without post-treatment (ⓑ of FIG. 1), the particles due to the formation of lithium compounds in the washed state after synthesis (ⓐ in FIG. 1) are distributed on the surface. The roughness can be seen.
이와 마찬가지로, 후처리를 통해(ex-situ) 리튬 화합물 코팅층을 표면에 생성한 경우(도 1의 ⓓ)와 코팅되지 않은 상용 리튬 코발트 산화물(도 1의 ⓒ)에 비해 표면이 미세하게 층이 생기고 거친 것을 확인할 수 있다.Similarly, when the lithium compound coating layer is formed on the surface through ex-situ (ⓓ in FIG. 1) and the surface is finely formed compared to the commercially available uncoated lithium cobalt oxide (ⓒ in FIG. 1). You can see the roughness.
실험예 2Experimental Example 2
상기 합성예 1과 4에 따라 각각 후처리 없이(in-situ) 리튬 화합물을 표면에 코팅한 경우와 후처리를 통해(ex-situ) 리튬 화합물을 코팅한 경우를 코팅 전 시료와 함께 XRD로 결정구조를 비교하였으며, 이를 하기 도 2에 나타내었다.According to Synthesis Examples 1 and 4, the case of coating the lithium compound on the surface and the after-treatment (ex-situ) on the surface of the lithium compound was determined as XRD together with the sample before coating, respectively. The structure was compared, which is shown in FIG. 2.
하기 도 2에서 보는 바와 같이, 합성 후 세척을 통해 표면을 깨끗하게 만든 상태(Synthesized & washed)나 상용화 되고 있는(pristine, commercial) 리튬 코발트 산화물의 경우 XRD 패턴에서 리튬 코발트 산화물 이외에 다른 상(phase)이 없이 말끔한 것을 볼 수 있다.As shown in FIG. 2, in the case of lithium cobalt oxide in which the surface is cleaned (synthesized & washed) or commercialized (pristine, commercial) through post-synthesis washing, a phase other than lithium cobalt oxide is different in the XRD pattern. You can see the neat without.
반면에, 후처리 없이(in-situ) 코팅하거나 후처리를 통해(ex-situ) 코팅한 경우 모두 강한 결정성을 띠는 리튬 코발트 산화물과 함께 약하지만 리튬 화합물 중 하나인 리튬 카보네이트(탄산 리튬, lithium carbonate(Li2CO3))가 불순물처럼 생긴 것을 명확히 확인할 수 있다. 열처리시에 탄산가스(CO2)를 포함한 분위기를 만들게 되면 잔류 리튬이 탄산가스와 반응하여 리튬 카보네이트가 만들어지게 된다.On the other hand, both in-situ coated and ex-situ coated lithium carbonate (lithium carbonate, which is one of the lithium compounds with weak cobalt oxide with strong crystallinity) Lithium carbonate (Li 2 CO 3 )) is clearly seen as an impurity. When an atmosphere containing carbon dioxide (CO 2 ) is formed during the heat treatment, residual lithium reacts with the carbon dioxide to form lithium carbonate.
실험예 3Experimental Example 3
상기 합성예 1과 4에 따라 각각 후처리 없이(in-situ) 리튬 화합물을 표면에 코팅한 경우와 후처리를 통해(ex-situ) 리튬 화합물을 코팅한 경우를 코팅 전 시료와 함께 IR 분광법으로 구조를 분석 및 비교하였으며, 이를 하기 도 3에 나타내었다.According to Synthesis Examples 1 and 4, the case where the lithium compound was coated on the surface and the after-treatment (ex-situ) was coated on the surface by IR spectroscopy with the sample before coating, respectively The structure was analyzed and compared, which is shown in FIG. 3.
하기 도 3에서 보는 바와 같이, 합성 후 세척을 통해 표면을 깨끗하게 만든 상태(Synthesized & washed)나 상용화 되고 있는(pristine, commercial) 리튬 코발트 산화물에서는 존재하지 않던 피크가 후처리 없이(in-situ) 코팅하거나 후처리를 통해(ex-situ) 코팅한 시료에서 모두 860 cm-1 부근, 1490 cm-1 부근 그리고 1520 cm-1 부근에서 리튬 카보네이트에 해당하는 피크가 생긴 것을 볼 수 있다.As shown in FIG. 3, the peaks that did not exist in the lithium cobalt oxide (Synthesized & washed) or commercialized (pristine, commercial) after the synthesis was washed in-situ coating. It can be seen that the peaks corresponding to lithium carbonate were formed in all of the samples coated or ex-situ coated around 860 cm −1, around 1490 cm −1 , and around 1520 cm −1 .
실험예 4Experimental Example 4
상기 합성예 1에서 리튬과 코발트의 비율 조절을 통해 합성된 리튬 화합물이 코팅된 리튬 코발트 산화물 활물질들의 전기화학적 충방전 특성을 비교하였다. In the synthesis example 1, the electrochemical charge and discharge characteristics of the lithium cobalt oxide active materials coated with the lithium compound synthesized by controlling the ratio of lithium and cobalt were compared.
리튬 소스인 리튬 전구체의 양을 10 wt%, 20 wt%, 30 wt%로 각각 늘려 리튬 코발트 산화물 활물질을 합성할 때, 합성에 필요한 리튬을 제외한 나머지 리튬은 불순물로 작용하게 되어 리튬 카보네이트가 잔류하게 된다. 잔류 리튬의 양에 따라 표면에 존재하는 리튬 카보네이트의 양이 변하게 되고, 리튬 카보네이트 코팅층에 의해서 하기 도 4와 같이 전기화학적 특성이 차이를 보이게 된다.When synthesizing a lithium cobalt oxide active material by increasing the amount of lithium precursor, a lithium source, to 10 wt%, 20 wt%, and 30 wt%, respectively, lithium, except lithium required for synthesis, acts as an impurity, causing lithium carbonate to remain. do. The amount of lithium carbonate present on the surface is changed according to the amount of residual lithium, and the electrochemical properties are shown to be different by the lithium carbonate coating layer as shown in FIG. 4.
실험예 5Experimental Example 5
상기 합성예 1에서 리튬과 코발트의 비율을 1.2 : 1로 합성한 리튬 화합물이 코팅된 활물질과 표면에 코팅이 되어있지 않은 리튬 코발트 산화물 활물질에 대한 전고체 전지의 전기화학적 충방전 특성을 비교하였다.In the synthesis example 1, the electrochemical charge and discharge characteristics of the all-solid-state battery for the lithium cobalt oxide active material coated with a lithium compound coated with a lithium compound having a ratio of 1.2: 1 to lithium cobalt oxide were compared.
통상적으로 고온 합성 중에 리튬 휘발로 인한 손실을 보상하기 위해리튬 소스인 리튬 전구체를 과량으로 하여 합성하게 되고, 이때 분위기에 따라 잔류 리튬은 다른 전구체들과 반응하여 대게 리튬 카보네이트로 잔류하게 된다. 이 때 액체 전해질을 사용한 리튬 이차전지에서는 리튬 카보네이트가 불순물로 여겨지게 되어 셀 특성의 열화가 발생한다.Typically, in order to compensate for the loss due to volatilization during high temperature synthesis, a lithium source, which is a lithium source, is synthesized in an excess amount, and depending on the atmosphere, the remaining lithium reacts with other precursors and usually remains as lithium carbonate. At this time, in a lithium secondary battery using a liquid electrolyte, lithium carbonate is regarded as an impurity, causing deterioration of cell characteristics.
반면, 동일한 방법으로 합성 후 고체 전해질을 사용하여 구성된 리튬 이차전지에서는 활물질의 전이금속 원소의 확산으로 인한 저항층 형성 또는 포텐셜 차이로 인한 리튬 결핍층 형성을 억제시키고 활물질과 전해질의 향상된 접촉면적으로 인한 넓은 리튬이온의 확산 경로를 유도하여 하기 도 5에서 보는 바와 같이 원활한 충방전이 이루어질 수 있음을 볼 수 있다.On the other hand, in the lithium secondary battery constructed using a solid electrolyte after synthesis in the same way, the formation of the resistive layer due to the diffusion of the transition metal element of the active material or the formation of a lithium deficient layer due to the potential difference and the improved contact area between the active material and the electrolyte It can be seen that a smooth charge and discharge can be made as shown in Figure 5 by inducing a diffusion path of a wide lithium ion.
실험예 6Experimental Example 6
상기 합성예 1에 따라 리튬 화합물의 비율을 달리하여 코팅한 후의 리튬 코발트 산화물에 대한 전고체 전지의 전기화학적 충방전 수명특성을 나타내었다.According to Synthesis Example 1, the electrochemical charge and discharge life characteristics of the all-solid-state battery with respect to the lithium cobalt oxide after coating with different proportions of the lithium compound were shown.
하기 도 5에서 확인할 수 있는 바와 같이, 코팅하지 않았을 때 전고체 전지에서는 충방전이 제대로 이루어지지 않는 것에 비하여 표면에 리튬 화합물이 코팅된 리튬 코발트 산화물 활물질은 전기화학적으로 안정적인 수명 특성을 보이는 것을 확인하였다. 또한, 하기 도 6에서 확인할 수 있는 바와 같이, 합성시 표면에 코팅된 리튬 산화물의 양에 따라 충방전 특성이 다르게 보이고 그 수명 특성 또한 차이가 있는 것을 확인하였다.As can be seen in Figure 5, when not coated in the all-solid-state battery, the lithium cobalt oxide active material coated with a lithium compound on the surface was confirmed that the electrochemically stable life characteristics as compared to not properly made . In addition, as can be seen in Figure 6, it was confirmed that the charge-discharge characteristics are different depending on the amount of lithium oxide coated on the surface during synthesis, the life characteristics are also different.
실험예 7Experimental Example 7
상기 합성예 2에 따라 리튬 전구체를 달리해서 합성 및 리튬 화합물을 코팅한 후의 리튬 코발트 산화물에 대한 전고체 전지의 전기화학적 충방전 특성을 나타내었다.According to Synthesis Example 2, the electrochemical charge and discharge characteristics of the all-solid-state battery with respect to lithium cobalt oxide after the synthesis and coating of the lithium compound with different lithium precursors were shown.
하기 도 7에서 보는 바와 같이, 코팅하기 전과 비교하여 리튬 전구체를 변화시키더라도 표면에 리튬 화합물을 코팅함에 있어 문제가 없고, 그 정도는 차이가 있지만 리튬 전구체를 달리하여 활물질의 전이금속 원소의 확산으로 인한 저항층 형성 또는 포텐셜 차이로 인한 리튬 결핍층 형성을 억제시키고 활물질과 전해질의 향상된 접촉면적으로 인한 넓은 리튬이온의 확산 경로를 유도하여 정상적으로 전기화학적 충방전이 정상적으로 이루어지는 것을 확인할 수 있다.As shown in FIG. 7, there is no problem in coating the lithium compound on the surface even if the lithium precursor is changed as compared with before coating, but there is a difference in the diffusion of transition metal elements of the active material by varying the lithium precursor. It can be confirmed that electrochemical charging and discharging is normally performed by suppressing the formation of the resistive layer or the formation of the lithium deficient layer due to the potential difference and inducing the diffusion path of the wide lithium ions due to the improved contact area between the active material and the electrolyte.
실험예 8Experimental Example 8
상기 합성예 3에 따라 리튬 코발트 산화물을 리튬 니켈-코발트 산화물활물질(LiNi0.02Co0.98O2)로 바꾸어 합성 및 코팅하였을 때의 전고체 전지의 전기화학적 충방전 특성을 비교하였다.According to Synthesis Example 3, the electrochemical charge and discharge characteristics of the all-solid-state battery when the lithium cobalt oxide was changed to lithium nickel-cobalt oxide active material (LiNi 0.02 Co 0.98 O 2 ) and synthesized and coated were compared.
리튬 코발트 산화물 활물질과 마찬가지로 코팅 전후로 전기화학적 충방전 특성이 차이를 보이는 것을 확인할 수 있다. 이를 통해 합성예 1의 리튬 코발트 산화물 활물질 이외의 다른 활물질에도 적용할 수 있음을 확인하였다.Like the lithium cobalt oxide active material it can be seen that the electrochemical charge and discharge characteristics show a difference before and after coating. This confirmed that it can be applied to other active materials other than the lithium cobalt oxide active material of Synthesis Example 1.
실험예 9Experimental Example 9
상기 합성예 4에 따라 다양한 리튬 전구체로 상용화된 리튬 코발트 산화물 활물질의 표면에 리튬 화합물을 후공정으로 코팅을 한 것을 적용한 전고체 전지의 전기화학적 충방전 특성을 비교하였다.According to Synthesis Example 4, the electrochemical charge and discharge characteristics of the all-solid-state battery to which a lithium compound was coated on a surface of a lithium cobalt oxide active material commercialized with various lithium precursors by a post-process was compared.
코팅을 하지 않았을 때와의 비교를 통해 리튬 소스로 여러 가지 전구체를 사용하여 코팅을 하더라도 표면에 리튬 화합물 코팅을 통해 전해질과의 활물질의 전이금속 원소의 확산으로 인한 저항층 형성 또는 포텐셜 차이로 인한 리튬 결핍층 형성을 억제시키고 활물질과 전해질의 향상된 접촉면적으로 인한 넓은 리튬이온의 확산 경로를 유도하여 주는 것을 확인하였다.Lithium due to resistance layer formation or potential difference due to diffusion of transition metal elements of the active material with electrolyte through the lithium compound coating on the surface, even if the coating using various precursors as a lithium source through comparison with no coating It was confirmed that it inhibits the formation of the deficient layer and induces a diffusion path of wide lithium ions due to the improved contact area between the active material and the electrolyte.
실험예 10Experimental Example 10
상기 합성예 4에 따라 여러 가지 리튬 전구체로 상용화된 리튬 코발트 산화물 활물질의 표면에 리튬 화합물 코팅을 한 것 중에서, 리튬 전구체를 리튬 하이드록사이드로 코팅한 시료에 대해 전고체 전지의 전기화학적 충방전 율속 특성을 비교하였다.The electrochemical charge and discharge rate of an all-solid-state battery with respect to a sample coated with lithium hydroxide with a lithium compound coating on the surface of a lithium cobalt oxide active material commercialized with various lithium precursors according to Synthesis Example 4 The characteristics were compared.
코팅 전후의 시료를 비교함으로써 리튬 화합물이 표면에 있을 때 수명특성이 향상될 뿐만 아니라 율속 특성 또한 향상되면서 배터리의 출력특성 또한 향상시킬 수 있음을 확인하였다.By comparing the samples before and after coating, it was confirmed that not only the lifespan characteristics were improved when the lithium compound was on the surface, but also the rate characteristics were improved, and the battery output characteristics were also improved.
실험예 11Experimental Example 11
상기 합성예 5에 따라 상용화된 리튬 니켈-코발트-망간 산화물 활물질의 표면에 리튬 화합물을 코팅한 시료에 대해 코팅하지 않은 상용 리튬-니켈-코발트-망간 산화물 활물질과 함께 전고체 전지의 전기화학적 충방전 특성을 비교하였다.Electrochemical charge and discharge of an all-solid-state battery together with a commercially available lithium-nickel-cobalt-manganese oxide active material not coated on a sample coated with a lithium compound on the surface of the lithium nickel-cobalt-manganese oxide active material commercialized according to Synthesis Example 5. The characteristics were compared.
상용 리튬 니켈-코발트-망간 산화물 활물질에 후처리를 통해 리튬 화합물 코팅 후 고체 전해질을 사용한 전고상 전지를 제조하였을 때의 전기화학적 충방전 특성을 비교하였다. 액체 전해질을 사용했을 때는 높은 용량과 안정적인 충방전 특성을 나타내는 상용 리튬 니켈-코발트-망간 산화물 활물질을 사용하였음에도 후처리를 통한 리튬 화합물 코팅을 실시하지 않은 경우 전고체 전지에서는 낮은 용량을 보였으며, 리튬 화합물을 코팅한 후에는 높은 용량을 보이는 것을 확인하였다.The electrochemical charge and discharge characteristics of the all-solid-state battery using a solid electrolyte after the lithium compound coating after the commercial lithium nickel-cobalt-manganese oxide active material was coated were compared. When the liquid electrolyte was used, although a commercial lithium nickel-cobalt-manganese oxide active material exhibiting high capacity and stable charge and discharge characteristics was used, all the solid-state batteries showed low capacity when the lithium compound coating was not applied after the post-treatment. After coating the compound it was confirmed to show a high capacity.
이를 통해 리튬 코발트 산화물 활물질뿐만 아니라 다른 활물질에서도 리튬 화합물 코팅으로 전기화학적 특성을 향상시킬 수 있음을 확인하였다.Through this, it was confirmed that not only the lithium cobalt oxide active material but also other active materials can improve the electrochemical properties by coating the lithium compound.
실험예 12Experimental Example 12
상기 합성예 5에 따라 상용화된 리튬 니켈-코발트-망간 산화물 활물질의 표면에 리튬 화합물을 코팅한 시료에 대해 코팅하지 않은 상용 리튬-니켈-코발트-망간 산화물 활물질과 함께 전고체 전지의 전기화학적 충방전 수명 특성을 비교하였다.Electrochemical charge and discharge of an all-solid-state battery together with a commercially available lithium-nickel-cobalt-manganese oxide active material not coated on a sample coated with a lithium compound on the surface of the lithium nickel-cobalt-manganese oxide active material commercialized according to Synthesis Example 5. Life characteristics were compared.
상기 실험예 11에서 확인한 향상된 전기화학적 특성이 얼마나 지속되는지 수명 특성을 확인하기 위하여 동일한 조건에서 50회의 충방전을 반복하여 진행했을 때, 코팅 전 시료의 경우 매우 낮은 용량이 지속적으로 보이는 것에 반해, 코팅 후의 시료는 50회의 충방전 후에도 높은 용량이 지속됨을 확인하였다. When repeated charging and discharging was repeated 50 times under the same conditions to confirm how long the improved electrochemical properties confirmed in Experimental Example 11 lasted, a very low capacity was observed in the case of the sample before coating. The later samples were confirmed to maintain high capacity even after 50 charge / discharge cycles.
이를 통해 리튬 화합물 코팅이 전기화학적 충방전 수명특성 또한 향상시킬 수 있음을 확인하였다.It was confirmed that the lithium compound coating can also improve the electrochemical charge and discharge life characteristics.
본 발명에 따른 전고체 리튬 이차전지의 양극 활물질은 리튬 화합물로 이루어진 코팅층이 입자 표면을 둘러싸면서 형성되어 있는 것을 특징으로 하고, 이러한 코팅층이 황화물계 고체 전해질과 전극의 계면반응을 억제해주는 기능층으로 작용하여 전고체 리튬 이차 전지 특성을 크게 향상시킬 수 있어 산업적으로 유용하게 이용할 수 있다.The positive electrode active material of the all-solid-state lithium secondary battery according to the present invention is characterized in that the coating layer made of a lithium compound is formed surrounding the particle surface, the coating layer is a functional layer to suppress the interfacial reaction between the sulfide-based solid electrolyte and the electrode By working, it is possible to greatly improve the characteristics of the all-solid-state lithium secondary battery can be useful industrially.

Claims (11)

  1. 하기 [화학식 1]로 표시되는 산화물 및 상기 산화물 입자의 표면을 둘러싸면서 형성된 리튬 화합물 코팅층을 포함하는 전고체 리튬 이차전지용 양극 활물질:A cathode active material for an all-solid-state lithium secondary battery comprising an oxide represented by the following [Formula 1] and a lithium compound coating layer formed while surrounding the surface of the oxide particles:
    [화학식 1][Formula 1]
    Li1+X(M)O2 Li 1 + X (M) O 2
    상기 [화학식 1]에서, M은 Co, Mn 및 Ni 중에서 선택되는 1종 이상을 포함한 전이금속 또는 이들의 혼합물이고, X는 0 < X < 1이다.In Formula 1, M is a transition metal or a mixture thereof including at least one selected from Co, Mn, and Ni, and X is 0 <X <1.
  2. 제1항에 있어서,The method of claim 1,
    상기 리튬 화합물 코팅층은 리튬하이드록사이드(LiOH)를 포함한 리튬염 및 리튬카보네이트(Li2CO3) 중에서 선택된 1종 이상으로 이루어진 것을 특징으로 하고,The lithium compound coating layer is characterized by consisting of at least one selected from lithium salts including lithium hydroxide (LiOH) and lithium carbonate (Li 2 CO 3 ),
    상기 리튬염은 리튬나이트레이트, 리튬하이드록사이드, 리튬시트레이트, 리튬아세테이트, 리튬설페이트 및 리튬카보네이트 중에서 선택되는 1종 이상인 것을 특징으로 하는 전고체 리튬 이차전지용 양극 활물질.The lithium salt is a cathode active material for an all-solid lithium secondary battery, characterized in that at least one selected from lithium nitrate, lithium hydroxide, lithium citrate, lithium acetate, lithium sulfate and lithium carbonate.
  3. 제1항에 있어서,The method of claim 1,
    상기 X는 0.10 내지 0.20 범위의 실수인 것을 특징으로 하는 전고체 리튬 이차전지용 양극 활물질.Wherein X is a real number in the range of 0.10 to 0.20 positive electrode active material for an all-solid lithium secondary battery.
  4. 황화물계 고체 전해질 및 제1항에 따른 양극 활물질을 포함하는 전극을 포함하는 전고체 리튬 이차전지.An all-solid-state lithium secondary battery comprising an electrode comprising a sulfide-based solid electrolyte and the cathode active material according to claim 1.
  5. (a) 리튬 전구체와 금속염을 1.10 : 1 내지 1.50 : 1의 몰비로 증류수에 용해 후 혼합하여 혼합용액을 수득하는 단계;(a) dissolving a lithium precursor and a metal salt in distilled water at a molar ratio of 1.10: 1 to 1.50: 1 to obtain a mixed solution by mixing;
    (b) 상기 혼합용액을 가열하고, 교반한 후 용매를 증발시키면서 건조하는 단계; 및(b) heating the mixed solution, stirring and drying the solvent while evaporating; And
    (c) 상기 건조하는 단계 이후 600-1000 ℃에서 열처리하는 단계;를 포함하는 하기 [화학식 1]로 표시되는 전고체 리튬 이차전지용 양극 활물질의 제조방법:(C) a method of producing a cathode active material for an all-solid-state lithium secondary battery represented by the following [Formula 1] comprising the step of heat treatment at 600-1000 ℃ after the drying step:
    [화학식 1][Formula 1]
    Li1+X(M)O2 Li 1 + X (M) O 2
    상기 [화학식 1]에서, 상기 M은 Co, Mn 및 Ni 중에서 선택되는 1종 이상을 포함한 전이금속 또는 이들의 혼합물이고, X는 0 < X < 1이고,In Formula 1, M is a transition metal or a mixture thereof including at least one selected from Co, Mn, and Ni, and X is 0 <X <1.
    상기 [화학식 1]로 표시되는 전고체 리튬 이차전지용 양극 활물질의 표면은 리튬 화합물 코팅층을 둘러싸여 있으며,The surface of the positive electrode active material for an all-solid-state lithium secondary battery represented by the above [Formula 1] is surrounded by a lithium compound coating layer,
    상기 리튬 화합물 코팅층은 상기 양극 활물질의 합성과 동시에 표면에 형성되는 것을 특징으로 한다.The lithium compound coating layer is formed on the surface simultaneously with the synthesis of the positive electrode active material.
  6. 제5항에 있어서,The method of claim 5,
    상기 리튬 전구체는 리튬나이트레이트, 리튬하이드록사이드, 리튬시트레이트, 리튬아세테이트, 리튬설페이트 및 리튬카보네이트 중에서 선택되고,The lithium precursor is selected from lithium nitrate, lithium hydroxide, lithium citrate, lithium acetate, lithium sulfate and lithium carbonate,
    상기 금속염은 Co, Mn 및 Ni 중에서 선택되는 1종 이상을 포함하는 전이금속 또는 이들의 혼합물의 질산염, 아세트산염 또는 시트르산염 중에서 선택되는 1종 이상인 것을 특징으로 하는 전고체 리튬 이차전지용 양극 활물질의 제조방법.The metal salt is a positive electrode active material for an all-solid-state lithium secondary battery, characterized in that at least one selected from nitrates, acetates or citrates of transition metals or mixtures thereof including at least one selected from Co, Mn and Ni. Way.
  7. 제5항에 있어서,The method of claim 5,
    상기 (b) 단계는 40-250 ℃ 온도로 가열하여 수행되는 것을 특징으로 하는 전고체 리튬 이차전지용 양극 활물질의 제조방법.The step (b) is a method for producing a positive electrode active material for an all-solid lithium secondary battery, characterized in that carried out by heating to a temperature of 40-250 ℃.
  8. 제5항에 있어서,The method of claim 5,
    상기 리튬 화합물 코팅층은 리튬하이드록사이드(LiOH)를 포함한 리튬염 및 리튬카보네이트(Li2CO3) 중에서 선택된 1종 이상으로 이루어진 것을 특징으로 하고,The lithium compound coating layer is characterized by consisting of at least one selected from lithium salts including lithium hydroxide (LiOH) and lithium carbonate (Li 2 CO 3 ),
    상기 리튬염은 리튬나이트레이트, 리튬하이드록사이드, 리튬시트레이트, 리튬아세테이트, 리튬설페이트 및 리튬카보네이트 중에서 선택되는 1종 이상인 것을 특징으로 하는 전고체 리튬 이차전지용 양극 활물질의 제조방법.The lithium salt is a method for producing a positive electrode active material for an all-solid lithium secondary battery, characterized in that at least one selected from lithium nitrate, lithium hydroxide, lithium citrate, lithium acetate, lithium sulfate and lithium carbonate.
  9. 제8항에 있어서,The method of claim 8,
    상기 리튬 화합물 코팅층은 리튬카보네이트(Li2CO3)이고, 상기 리튬카보네이트는 상기 (c) 단계의 열처리가 탄산가스(CO2) 또는 탄산가스를 포함한 복합 가스 분위기 분위기에 수행되는 경우에 형성된 것을 특징으로 하는 전고체 리튬 이차전지용 양극 활물질의 제조방법.The lithium compound coating layer is lithium carbonate (Li 2 CO 3 ), the lithium carbonate is characterized in that formed in the case where the heat treatment of the step (c) is performed in a complex gas atmosphere atmosphere containing carbon dioxide (CO 2 ) or carbon dioxide gas The manufacturing method of the positive electrode active material for all-solid-state lithium secondary batteries which are used.
  10. (a) 리튬 전구체를 물에 용해하고 교반하여 리튬 전구체 용액을 수득하는 단계;(a) dissolving a lithium precursor in water and stirring to obtain a lithium precursor solution;
    (b) 상기 리튬 전구체 용액에 하기 [화학식 1]로 표시되는 산화물 활물질을 분산시켜 혼합 용액을 수득하는 단계;(b) dispersing an oxide active material represented by the following [Formula 1] in the lithium precursor solution to obtain a mixed solution;
    (c) 상기 혼합용액을 건조 후, 600-1000 ℃에서 열처리하는 단계;를 포함하고,(c) drying the mixed solution and heat-treating at 600-1000 ° C .;
    상기 산화물 활물질의 표면은 리튬 화합물 코팅층을 둘러싸여 있는 것을 특징으로 하는 전고체 리튬 이차전지용 양극 활물질의 제조방법:Method for producing a cathode active material for an all-solid lithium secondary battery, characterized in that the surface of the oxide active material is surrounded by a lithium compound coating layer:
    [화학식 1][Formula 1]
    Li1+X(M)O2 Li 1 + X (M) O 2
    상기 [화학식 1]에서, 상기 M은 Co, Mn 및 Ni 중에서 선택되는 1종 이상을 포함한 전이금속 또는 이들의 혼합물이고, X는 0 < X < 1이다.In Formula 1, M is a transition metal or a mixture thereof including at least one selected from Co, Mn, and Ni, and X is 0 <X <1.
  11. 제10항에 있어서,The method of claim 10,
    상기 리튬 전구체는 리튬나이트레이트, 리튬하이드록사이드, 리튬시트레이트, 리튬아세테이트, 리튬설페이트 및 리튬카보네이트 중에서 선택되는 것을 특징으로 하고,The lithium precursor is selected from lithium nitrate, lithium hydroxide, lithium citrate, lithium acetate, lithium sulfate and lithium carbonate,
    상기 리튬 화합물 코팅층은 리튬하이드록사이드(LiOH)를 포함한 리튬염 및 리튬카보네이트(Li2CO3) 중에서 선택된 1종 이상으로 이루어진 것을 특징으로 하고,The lithium compound coating layer is characterized by consisting of at least one selected from lithium salts including lithium hydroxide (LiOH) and lithium carbonate (Li 2 CO 3 ),
    상기 리튬염은 리튬나이트레이트, 리튬하이드록사이드, 리튬시트레이트, 리튬아세테이트, 리튬설페이트 및 리튬카보네이트 중에서 선택되는 1종 이상인 것을 특징으로 하는 전고체 리튬 이차전지용 양극 활물질의 제조방법.The lithium salt is a method for producing a positive electrode active material for an all-solid lithium secondary battery, characterized in that at least one selected from lithium nitrate, lithium hydroxide, lithium citrate, lithium acetate, lithium sulfate and lithium carbonate.
PCT/KR2014/011508 2013-11-29 2014-11-27 Active material for all-solid lithium secondary battery, method for manufacturing same, and all-solid lithium secondary battery comprising same WO2015080502A1 (en)

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